The week of May 22-26 saw the arrival of some much needed precipitation to parts of Alberta and Saskatchewan, but hot weather up to May 21 across most of the prairies has affected insect development so far this spring.
Grasshoppers thrive in warm, dry conditions and we continue to hear about high numbers of nymphs along roadsides and field edges. Diamondback moths have been captured in pheromone traps across the prairies, generally in low numbers. In preparation for bertha armyworm monitoring, we ran the model for pupal development this week and unsurprisingly, development is ahead of schedule. For more information, check out the posts in the Weekly Update! The Insect of the Week is about parasitoids of cutworms this week – read on and check out the links for more information. Finally, Dr. Kevin Floate has written a new book about dung beetles that is available for free download!
The prairie-wide maps summarizing the results from the 2022 growing season are online and available for review, as are the historical insect pest distribution maps. These prairie-wide geospatial maps offer insight into potential risk and help growers prioritize their scouting lists.
Remember, insect Monitoring Protocols containing helpful insect pest biology, how and when to plan for in-field scouting, and even thresholds to help support in-field management decisions are all available for review or download.
Questions or problems accessing the contents of this Weekly Update? Please contact Dr. Meghan Vankosky (meghan.vankosky@agr.gc.ca) to get connected to our information. Past Weekly Updates, full of information and helpful links, can be accessed on our Weekly Update page.
***Special thanks to Mark Berry, AAFC-Geomatics, for providing up-to-date weather information for the prairies that is summarized here and used to predict insect development. Mark provides this information for every Weekly Update, but I’m new to running the website and have not yet figured out how to add him to the author list for the posts***
During the week of May 15-21 average prairie temperatures continued to be well above average. The average daily temperature was 4°C warmer than normal (Fig. 1). The warmest temperatures were observed across Alberta and western Saskatchewan. Dawson Creek, BC was 8°C warmer than average temperatures for mid-May. The coolest weekly temperatures were observed over eastern Saskatchewan and Manitoba.
Figure 1. Seven-day average temperature (°C) observed across the Canadian prairies for the period of May 15-21, 2023.
Average temperatures over the past 30 days (April 22 – May 21, 2023) have been 3°C above normal with the warmest values being reported for Alberta and western Saskatchewan (Fig. 2).
Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of April 22-May 21, 2023.
Since April 1, the 2023 growing season has been coolest across eastern Saskatchewan and Manitoba (Fig. 3). Alberta temperatures continue to be above average. Relative to climate normals, growing season temperatures have been well above normal in the Peace River region. Fort Vermillion, AB has been 5°C warmer than normal and Fort St. John, BC has been 4°C above normal. Temperatures have been below normal for many locations in Manitoba. For example, the average temperature near Melita has been 2.25°C cooler than average.
Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to May 21, 2023.
Seven-day cumulative rainfall (May 15-21) was very low for Alberta and Saskatchewan (Fig. 4). Over the past 30 days (April 22 – May 21, 2023), rainfall has been minimal for Saskatchewan and Alberta (Fig. 5). For example, Saskatoon has had 12 mm of rain in that time, which is only 9% of what the Saskatoon area normally receives in the same period. On average, the prairie region has received about 40% of the precipitation normally expected for this time of year. For more information, visit the Agriculture and Agri-Food Canada Agroclimate site (https://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true).
Figure 4. Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of May 15-21, 2023. Figure 5. 30-day average cumulative rainfall (mm) observed across the Canadian prairies for the period of April 22-May 21, 2023.
Growing season rainfall has been below normal across most of the prairies so far in 2023 (Fig. 6). A large region, extending from Lethbridge to Saskatoon to the Peace River region continues to have well below normal rainfall accumulations (Fig. 6). Meadow Lake rainfall has been 34% of normal and Kindersley has reported only 15 mm (42% of normal).
Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to May 21, 2023.
Agriculture and Agri-Food Canada (AAFC; Ross Weiss, Meghan Vankosky) and Environment and Climate Change Canada (ECCC; Serge Trudel) have been working together to study the potential of trajectories for monitoring insect movements since the late 1990s. Trajectory models are used to deliver an early-warning system for the origin and destination of migratory invasive species, such as diamondback moth.
‘Reverse trajectories’ refer to air currents that are tracked back in time from specified Canadian locations over a five-day period prior to their arrival date. Of particular interest are those trajectories that, prior to their arrival in Canada, originated over northwestern and southern USA and Mexico, anywhere diamondback moth populations overwinter and adults are actively migrating. If diamondback moth adults are present in the air currents that originate from these southern locations, the moths may be deposited on the Prairies at sites along the trajectory, depending on the local weather conditions at the time that the trajectories pass over our area (e.g., rain showers, etc.). Reverse trajectories are the best available estimate of the ”true” 3D wind fields at a specific point. They are based on observations, satellite and radiosonde data.
Wind Trajectories, May 1 to May 23, 2023:
Since May 1, 2023, the majority of reverse trajectories that have crossed the prairies originated from the Pacific Northwest (Idaho, Oregon and Washington) (Fig. 1). Very few reverse trajectories that originated in Mexico, California or Texas passed over the Canadian prairies between May 1 and May 23. No reverse trajectories, originating over Oklahoma or Texas crossed over the prairies this week.
Figure 1. The average number (based on a 5-day running average) of reverse trajectories (RT) that have crossed the prairies for the period of May 1-23, 2023.
The majority of reverse trajectories originating in the Pacific Northwest have been reported to pass over south-central Alberta and southwestern Saskatchewan (Fig. 2).
Figure 2. Total number of dates with reverse trajectories originating over the Idaho, Oregon, and Washington that have crossed the prairies between April 1 and May 23, 2023.
Since April 1, reverse trajectories that originated in Kansas and Nebraska were reported to cross southeastern Saskatchewan and southern Manitoba (Fig. 3).
Figure 3. The total number of dates with reverse trajectories originating over Kansas and Nebraska that have crossed the prairies between May 1 and May 23, 2023.
Model simulations were used to estimate development of grasshoppers as of May 21, 2023. Compared with average spring temperatures, well above normal temperatures in Alberta and western Saskatchewan have contributed to rapid grasshopper egg development (Fig. 1) that is well ahead of what we would expect at this time in an average growing season (Fig. 2). Average egg development for the prairies is 81% complete. The model predicts that egg development is well ahead of the long-term value of 67% complete for this time of year. Cool conditions in Manitoba have resulted in slower development rates that are similar to long-term average development rates.
Figure 1. Predicted grasshopper (Melanoplus sanguinipes) embryological development across the Canadian prairies as of May 21, 2023. Figure 2. Long-term average predicted grasshopper (Melanoplus sanguinipes) embryological development across the Canadian prairies as of May 21, based on climate normals data.
As a result of above normal temperatures, model predictions indicate that grasshopper eggs have already started to hatch, especially in Alberta and western Saskatchewan (Fig. 3). Model simulations suggest that hatch rates are 15-35% across the Peace River region. This is well ahead of long-term average hatch rates and we already have reports of grasshopper nymphs found along roadsides and field edges in Alberta and Saskatchewan. Prairie farmers should be prepared to scout for grasshoppers for the next 2-3 weeks, especially if conditions remain warmer and drier than normal.
Figure 3. Predicted grasshopper (Melanoplus sanguinipes) hatch (%) across the Canadian prairies as of May 21, 2023.
Analysis of wind trajectory data (from Environment and Climate Change Canada) indicates that a number of upper air currents, originating over the USA Pacific Northwest, passed over Alberta and Saskatchewan during the last week of April and first three weeks of May. These wind currents could have been carrying adult diamondback moths into the prairies. In fact, adult diamondback moths have been collected in traps located across Alberta (information courtesy of Shelley Barkley, Alberta Agriculture and Irrigation) and Saskatchewan (information courtesy of Carter Peru and James Tansey, Saskatchewan Ministry of Agriculture) during the first three weeks of May.
DBM development can be rapid during periods of warm weather. This week, the diamondback moth model was initialized for May 1, 2023 and run to May 21. Though canola may not be present, model results indicate that females may have begun to lay eggs on cruciferous plants like volunteer canola and weeds. Larvae could now also be found feeding on these host plants. The model simulation indicates that populations near Grande Prairie, AB (Fig. 1) are likely to be more advanced in terms of development than populations near Cadillac, SK (Fig. 2) reflecting differences in growing season weather so far in 2023 at the two locations.
Figure 1. Predicted development of diamondback moth (Plutella xylostella) near Grande Prairie, AB as of May 21, 2023. Figure 2. Predicted development of diamondback moth (Plutella xylostella) near Cadillac, SK as of May 21, 2023 (Biofix date = May 1, 2023).
Spring Pheromone Trap Monitoring of Adult Males: Across the Canadian prairies, spring monitoring is initiated to acquire weekly counts of adult moths attracted to pheromone-baited delta traps deployed in fields. Weekly trap interceptions are observed to generate cumulative counts. Summaries or maps of cumulative male diamondback moth counts will be available for each province as the monitoring season progresses. These cumulative count estimates are broadly categorized to help producers prioritize and time in-field scouting for larvae.
In-Field Monitoring:Remove plants in an area measuring 0.1 m² (about 12″ square), beat them onto a clean surface and count the number of larvae dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
The life stages of diamondback moth, Plutella xylostella: (A) eggs, (B) early instar larva, (C) late instar larvae, (D) pupa, and (E) adult moth. Photo credit: Jonathon Williams, AAFC-Saskatoon (all pictures)
Based on model simulations, development of overwintered BAW pupae this spring (Fig. 1) is expected to be significantly ahead of normal for most of the prairies (Fig. 2). BAW pupal development in Alberta is 10-14 days faster than average development for this time of year.
Figure 1. Predicted bertha armyworm (Mamestra configurata) pupal development (%) across the Canadian prairies as of May 21, 2023. Figure 2. Long-term average predicted bertha armyworm (Mamestra configurata) pupal development (%) across the Canadian prairies as of May 21, 2023.
To best detect the initial flight of adult BAW, pheromone traps should be placed in fields when pupal development is 75-80% complete. This ensures that traps are deployed before adults emerge and the mating period begins. Based on current BAW development, as predicted by the model, it is advisable that pheromone traps in Alberta be placed in fields this week or early next week (week of May 29). Pheromone traps should be installed later next week in most of Saskatchewan. At trap sites in eastern Saskatchewan and Manitoba, the pheromone traps should be placed in fields before June 9th.
Provincial entomologists provide insect pest updates throughout the growing season. Visit the links below to read their updates and to find other valuable information about prairie crop insects and beneficial insects.
The first Manitoba Crop Pest Update for 2023 is now available! Looking for historical information? Links are available for past Updates too.
Watch for new issues of the Saskatchewan Crop Production News coming soon in 2023 and browse the articles from 2022 for information from the past.
Visit the Alberta Insect Pest Monitoring Network page for information about insect monitoring in Alberta, including live maps from the 2023 monitoring season for diamondback moth, bertha armyworm, cutworms and others.
Entomologist Dr. Kevin Floate aims to answer ‘what critters are found in a cow patty?’ and ‘what do they do?’ His hope is to spark the interest of ranchers and farmers, and to stir the minds of students studying insects. In his own words, ‘This is the guide I wish I had when I started my career.’
Cover and sample content of Cow Patty Critters
Insects serve an outsized role in many ecosystem services. For dung on Canadian pastures, there are over 300 species of insects helping to break down and cycle nutrients through the soil and food webs. Understanding what insects are present in a cow patty provides insights into livestock health and ecological processes.
Dr. Kevin Floate speaking about insects to a captivated audience. Photo credit: Cam Goater, University of Lethbridge
Download your copy of Cow Patty Critters in English or in French.
This new 224-page, full color guide provides the ‘doorway’ to learn more about the critters one can find in cow dung: how to identify them, how they can be beneficial, and additional information on the biology and morphology of multiple insect groups. Also included is an extensive reference list for those who wish to pursue detailed insect identification.
This is Week 2 of the 2023 Prairie Pest Monitoring Network Weekly Updates!
Spring weather continues to be hot and dry across the prairies, bringing some challenging conditions for #Plant2023. Please stay safe.
Grasshoppers thrive in warm, dry conditions and there are reports that first instar nymphs are already hatching. Diamondback moths are appearing in pheromone traps across the prairies, albeit in low numbers so far. For more information, check out the posts in the Weekly Update! The Insect of the Week is about cutworms this week – read on and check out the links for more information.
The prairie-wide maps summarizing the results from the 2022 growing season are online and available for review, as are the historical insect pest distribution maps. These prairie-wide geospatial maps offer insight into potential risk and help growers prioritize their scouting lists.
Remember, insect Monitoring Protocols containing helpful insect pest biology, how and when to target in-field scouting, and even thresholds to help support in-field management decisions are all available for review or download.
Questions or problems accessing the contents of this Weekly Update? Please contact Dr. Meghan Vankosky (meghan.vankosky@agr.gc.ca) to get connected to our information. Past Weekly Updates, full of information and helpful links, can be accessed on our Weekly Update page.
Similar to the previous week, this past week (May 8-14, 2023) was warmer and drier than normal. The average temperature across the prairies was 5°C warmer than normal (Fig. 1). This week, the warmest temperatures were observed across southern Manitoba, the northern Peace River region, and across a region that extended between Saskatoon and Edmonton. The coolest weekly temperatures were observed over southern regions of Alberta and Saskatchewan.
Figure 1. Seven-day average temperature (°C) observed across the Canadian prairies for the period of May 8-14, 2023.
Since April 1, the 2023 growing season has been marginally cooler than average across eastern Saskatchewan and Manitoba (Fig. 2). Alberta temperatures continue to be above average. Relative to climate normals, growing season temperatures have been well above normal in the Peace River region. Fort Vermillion has been 4.7°C warmer than normal and Manning has been 3°C warmer than normal.
Figure 2. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to May 14, 2023.
Seven-day cumulative rainfall was greatest across the southern prairies and central regions of Alberta (Fig. 3). Central regions of Saskatchewan received minimal rain over the past seven days. Growing season rainfall (April 1 to May 14) has been below normal across most of the prairies (Fig. 4). A large region, extending from Lethbridge to Saskatoon to the Peace River region has received well below normal rainfall accumulations so far in 2023.
Figure 3. Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of May 8-14, 2023.Figure 4. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to May 14, 2023.
Agriculture and Agri-Food Canada (AAFC; Ross Weiss, Meghan Vankosky) and Environment and Climate Change Canada (ECCC; Serge Trudel) have been working together to study the potential of trajectories for monitoring insect movements since the late 1990s. Trajectory models are used to deliver an early-warning system for the origin and destination of migratory invasive species, such as diamondback moth. In addition, plant pathologists have shown that trajectories can assist with the prediction of plant disease infestations and are also beginning to utilize these same data. We receive two types of model output from ECCC: reverse trajectories and forward trajectories.
‘Reverse trajectories’ refer to air currents that are tracked back in time from specified Canadian locations over a five-day period prior to their arrival date. Of particular interest are those trajectories that, prior to their arrival in Canada, originated over northwestern and southern USA and Mexico, anywhere diamondback moth populations overwinter and adults are actively migrating. If diamondback adults are present in the air currents that originate from these southern locations, the moths may be deposited on the Prairies at sites along the trajectory, depending on the local weather conditions at the time that the trajectories pass over our area (e.g., rain showers, etc.). Reverse trajectories are the best available estimate of the ”true” 3D wind fields at a specific point. They are based on observations, satellite and radiosonde data.
Wind Trajectory Summary to May 16, 2023
Since May 1, 2023, the majority of the reverse trajectories that have crossed the prairies originated from the Pacific Northwest (Idaho, Oregon and Washington) (Fig. 1).
Figure 1. The average number (based on a 5-day running average) of reverse trajectories (RT) that have crossed the prairies for the period of May 1-16, 2023.
Mexico, California and Texas – Very few reverse trajectories that originated from Mexico, California or Texas have passed over the Canadian prairies so far in May 2023.
Pacific Northwest (Idaho, Oregon, Washington) – The majority of Pacific Northwest reverse trajectories have been reported to pass over south-central Alberta and southwestern Saskatchewan (Fig. 2).
Figure 2. Total number of dates with reverse trajectories originating over the Idaho, Oregon, and Washington that have crossed the prairies between April 1 and May 16, 2023.
Oklahoma and Texas – Since April 1, reverse trajectories from Oklahoma and Texas were reported to cross the southern prairies (Fig. 3).
Figure 3. The total number of dates with reverse trajectories originating over Texas and Oklahoma that have crossed the prairies between May 1 and May 16, 2023.
Kansas and Nebraska – Since April 1, reverse trajectories were reported to cross southeastern Saskatchewan and southern Manitoba (Fig. 4).
Figure 4. The total number of dates with reverse trajectories originating over Kansas and Nebraska that have crossed the prairies between May 1 and May 16, 2023.
Model simulations were used to estimate development of grasshopper eggs as of May 14, 2023. Compared with average spring temperatures, temperatures in Alberta and western Saskatchewan have been well above average so far in 2023. Unseasonably warm temperatures continue to contribute to rapid grasshopper egg development (Fig. 1). Compared to egg development expected if temperatures were like long-term to climate normals (Fig. 2), egg development in 2023 is well ahead of average (Fig. 1). Cool conditions in Manitoba have resulted in slower development rates that are similar to long-term average development rates.
Figure 1. Predicted grasshopper (Melanoplus sanguinipes) embryological development across the Canadian prairies as of May 14, 2023. Figure 2. Long-term average predicted grasshopper (Melanoplus sanguinipes) embryological development across the Canadian prairies as of May 14, based on climate normals data.
As a result of above normal temperatures, model outputs predict that grasshopper eggs have already started to hatch across Alberta and western Saskatchewan (Fig. 3). We have received reports of grasshopper nymphs from both provinces. This spring, grasshopper eggs are hatching approximately 10 days earlier than normal. Areas with highest densities of adult grasshoppers in summer of 2022 overlap with regions with greatest predicted egg development so far in spring of 2023 (Fig. 4), including a large region extending from south of the Yellowhead Highway corridor to the Canada-USA border. Prairie farmers should be scouting for grasshoppers early this spring and summer, especially if conditions remain warmer and drier than normal over the next few weeks.
Figure 3. Predicted grasshopper (Melanoplus sanguinipes) hatch (%) across the Canadian prairies as of May 14, 2023.Figure 4. Estimated grasshopper population densities in late summer and early fall 2022 in western Canada; areas with high grasshopper densities in 2022 are at risk of high grasshopper densities and associated damage in 2023, based on knowledge of the life history of the primary pest species, including Melanoplus sanguinipes (migratory grasshopper) (map by Ross Weiss, AAFC-Saskatoon).
Test your grasshopper knowledge by taking the Canola Watchquiz!
It has been suggested the overwintering mortality of diamondback moth (DBM) is high on the prairies. DBM, carried on upper air currents, may be introduced to the prairies from overwintering sites in southern USA and the US Pacific Northwest. Analysis of wind trajectory data (from Environment and Climate Change Canada) indicated that a number of upper air currents, originating over the US Pacific Northwest, passed over the Peace River region during the last week of April and first two weeks of May. DBM development can be rapid during periods of warm weather. Shelley Barkley (Alberta Agriculture and Irrigation) reports that DBM adults have been collected from a number of traps across Alberta. In Alberta, trap captures of DBM have been highest near Grande Prairie. Similarly, Carter Peru and James Tansey (Saskatchewan Ministry of Agriculture) note that adult DBM have been collected on traps located across Saskatchewan.
During the growing season, results from the DBM monitoring program in Saskatchewan will be available here (scroll to the bottom of the page) and results from Alberta will be available here.
The life stages of diamondback moth, Plutella xylostella: (A) eggs, (B) early instar larva, (C) late instar larvae, (D) pupa, and (E) adult moth. Photo credit: Jonathon Williams, AAFC-Saskatoon (all pictures)
DBM were collected during the first and second weeks of May. Thus, the DBM model was initialized for May 1, 2023 and run to May 14. Though canola may not be present, results indicate that females may have started to lay eggs on brassicaceous plants (e.g., volunteer canola, flix weed) and larvae may have hatched from early-laid eggs. In the Grande Prairie area, for example, both eggs and first instar larvae may already be present (Fig. 1).
Figure 1. Predicted development of diamondback moth (Plutella xylostella) near Grande Prairie, AB as of May 14, 2023.
Welcome to the first Weekly Update for the 2023 growing Season!
As planting and insect scouting are just getting started, this Weekly Update focuses on two important insects to watch out for early in the season, grasshoppers and alfalfa weevil. The first Insect of the Week (which unfortunately did not get emailed out earlier this week) is a timely reminder to watch out for flea beetles.
The prairie-wide maps summarizing the results from the 2022 growing season are online and available for review, as are the historical insect pest distribution maps. These prairie-wide geospatial maps offer insight into potential risk and help growers prioritize their scouting lists.
Remember, insect Monitoring Protocols containing helpful insect pest biology, how and when to target in-field scouting, and even thresholds to help support in-field management decisions are all available for review or download.
Wishing everyone good weather and let the insect scouting begin!
Questions or problems accessing the contents of this Weekly Update? Please contact Dr. Meghan Vankosky (meghan.vankosky@agr.gc.ca) to get connected to our information. Past “Weekly Updates” can be accessed on our Weekly Update page.
Since April 1, the 2023 growing season has been cooler than average and marginally wetter than normal. It has been coolest across Manitoba and central Saskatchewan (Fig. 1). This past week (May 1-7, 2023), the average temperature across the prairies was 5°C warmer than normal (Fig. 2). Temperatures were warmest across Alberta and western Saskatchewan and cooler over eastern Saskatchewan and Manitoba.
Figure 1. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to May 7, 2023.Figure 2. Seven-day average temperature (°C) observed across the Canadian prairies for the period of May 1-7, 2023.
Growing season rainfall has been near normal across most of the prairies so far in 2023, with the greatest accumulations reported across southern Manitoba and Saskatchewan (Fig. 3). Between May 1 and May 7, 2023, the 7-day cumulative rainfall was marginal across most of the prairies (Fig. 4).
Figure 3. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to May 7, 2023.Figure 4. Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of May 1-7, 2023.
The grasshopper model predicts development of the migratory grasshopper (Melanoplus sanguinipes) and closely related species using biological parameters known for the pest species and environmental data observed across the Canadian prairies on a daily basis. Review lifecycle and damage information for this pest. Review the historical grasshopper maps based on late-summer adult in-field counts performed across the prairies. Results from the 2022 late-summer adult grasshopper survey are shown in Fig. 1.
Figure 1. Adult grasshopper densities in late summer of 2022.
Model simulations were used to estimate development of grasshopper eggs as of May 7, 2023. Compared with average spring temperatures, well above normal temperatures in Alberta and western Saskatchewan thus far this spring are predicted to result in rapid grasshopper egg development (Fig. 2). As a result, grasshopper egg development in 2023 is expected to be advanced as compared to egg development in average growing seasons (Fig. 3). Cool conditions in Manitoba have resulted in slower rates of egg development. Areas with the highest adult grasshopper densities in summer 2022 (Fig. 1) overlap with regions where egg development is predicted to be most advanced so far in spring 2023 (Fig. 2). Based on the 2022 survey, high densities were reported across a large region that extended south of the Yellowhead Highway corridor to the Canada-USA border (Fig. 1).
Prairie farmers should be prepared to scout for grasshoppers in spring and early summer this year, especially if conditions remain warmer and drier than normal.
Figure 2. Predicted grasshopper (Melanoplus sanguinipes) embryological development across the Canadian Prairies as of May 7, 2023.Figure 3. Long-term average predicted grasshopper (Melanoplus sanguinipes) embryological development across the Canadian prairies as of May 7, 2023, based on climate normals data.
The alfalfa weevil (AAW), Hypera postica, model predicts development using biological parameters known for the pest species and environmental data observed across the Canadian prairies on a daily basis. Review lifecycle and damage information for this pest.
Model simulations for alfalfa weevil (AAW), Hypera postica, indicate that oviposition should be underway across the prairies. Relative to eastern Saskatchewan and Manitoba, warmer temperatures in Alberta are predicted to have resulted in rapid development of alfalfa weevil populations. The following graphs indicate, based on potential number of eggs, that development of alfalfa weevil populations is greater near Lethbridge (Fig. 1) than Regina (Fig. 2). As of May 7, 2023, alfalfa weevil populations may have produced two or three times more eggs in the Lethbridge area than alfalfa weevil populations near Regina. The model predicts that hatch may occur across southern Alberta in mid-May and 10 days later across south-central Saskatchewan.
Figure 1. Predicted status of alfalfa weevil populations near Lethbridge, Alberta as of May 7, 2023.Figure 2. Predicted status of alfalfa weevil populations near Regina, Saskatchewan as of May 7, 2023.
In 2022, collaborators and contributors of the Prairie Pest Monitoring Network conducted surveys and monitoring for grasshoppers, bertha armyworm, wheat midge, wheat stem sawfly, pea leaf weevil, cabbage seedpod weevil, and diamondback moths. Over 5000 samples were collected (Figure 1) and we acknowledge the considerable and valuable contribution that all of our collaborators and volunteers made in 2022. We also thank the organizations that fund the Prairie Pest monitoring network and recognize the considerable in-kind contributions made by our provincial partners, including Alberta Agriculture and Irrigation, the Saskatchewan Ministry of Agriculture, and Manitoba Agriculture. Thank you to everyone!
To volunteer access to your farmland for insect, plant pathogen and disease surveys in Saskatchewan in 2023, please visit the Pest Monitoring In Saskatchewan Page.
Figure 1. Distribution of sampling points from the 2022 survey season.
Meghan Vankosky, Owen Olfert, John Gavloski, Shelley Barkley, James Tansey, Ross Weiss, Jennifer Otani
Bertha armyworm (Mamestra configurata) populations are monitored annually in western Canada using pheromone baited traps. These traps are maintained by volunteer growers and agronomists, and by provincial and federal entomologists. The protocol used to monitor bertha armyworm using pheromone traps was updated in spring 2019 and is available here. The monitoring program provides early warning of when regional population densities may be approaching economic thresholds. However, site-specific interpretation of trap counts is difficult because pheromone traps do not capture female moths and it is the females that decide where to lay eggs. In-field scouting for bertha armyworm larvae is required for accurate, local, population estimates, as described in the monitoring protocol.
Cumulative trap captures below 600 generally represent low risk to crop production. In 2022, the cumulative trap captures of male bertha armyworm were very low, with very few traps across the prairies capturing more than 300 moths (Figure 2). The monitoring results from 2022 were very similar to those from 2020 and 2021 (Figure 3).
Figure 2. The cumulative trap catch of adult male bertha armyworm (Mamestra configurata) in pheromone-baited traps across the prairies in 2022 (map by Ross Weiss, AAFC-Saskatoon).
Figure 3. The cumulative trap catch of adult male bertha armyworm (Mamestra configurata) in pheromone-baited traps across the prairies from 2018 to 2021 (maps by David Giffen, AAFC-Saskatoon).
This survey is funded through the AgriScience Program as part of the Canadian Agricultural Partnership, a federal, provincial, territorial initiative. Funders include Agriculture & Agri-Food Canada, Western Grains Research Foundation, SaskWheat, Manitoba Crop Alliance, Alberta Wheat Commission, SaskPulse, Manitoba Canola Growers, Prairie Oat Growers Association, SaskCanola, and Manitoba Pulse & Soybean Growers. The network of pheromone traps was implemented and monitored by Alberta Agriculture and Irrigation, Saskatchewan Ministry of Agriculture, Manitoba Agriculture, and Agriculture & Agri-Food Canada (AAFC).
Meghan Vankosky, Owen Olfert, James Tansey, John Gavloski, Shelley Barkley, Ross Weiss, Jennifer Otani
The grasshopper survey is conducted by estimating adult grasshopper densities in the late summer and early fall, usually in ditches alongside cereal fields. This survey estimates the number of adult grasshoppers capable of laying eggs before winter and contributes to an estimate of future risk, where high densities in the current year predict higher levels of risk to crops in the next growing season. However, weather and biotic factors may increase or reduce risk during a given growing season, and these are not incorporated into the map in Figure 4. Factors that lead to increased grasshopper populations include warm and dry conditions in late summer and fall; these encourage mating, egg laying, and egg development. Warm and dry conditions in the spring increase the survival of grasshopper hatchlings and the risk of crop damage. Cool and wet growing conditions have negative effects on grasshopper development. Therefore, actual levels of infestation in field crops may differ from those predicted by the fall survey because of regional variation in weather conditions and the grasshopper species present.
Recent dry conditions across the central and southern prairies have been ideal for grasshoppers. In 2022, grasshopper densities were greatest in the region south of the Yellowhead Highway corridor (Figure 4). Although the area with grasshopper infestation in 2022 was similar to that observed in 2021, population densities were greater in 2022 than in 2021. More widespread outbreaks were observed in 2022 (Figure 2) than in the last few years (Figure 5). Prairie farmers should be prepared to scout for grasshoppers in spring and early summer in 2023, especially if weather conditions remain warmer and drier than normal.
A protocol for grasshopper scouting is available on the Monitoring Protocol page.
Figure 4. Estimated grasshopper population densities in late summer and early fall 2022 in western Canada; areas with high grasshopper densities in 2022 are at risk of high grasshopper densities and associated damage in 2023, based on knowledge of the life history of the primary pest species, including Melanoplus sanguinipes (migratory grasshopper) (map by Ross Weiss, AAFC-Saskatoon).
Figure 5. Estimated grasshopper population densities from annual surveys conducted from 2018-2021 (maps by David Giffen, AAFC-Saskatoon).
This survey is funded through the AgriScience Program as part of the Canadian Agricultural Partnership, a federal, provincial, territorial initiative. Funders include Agriculture & Agri-Food Canada, Western Grains Research Foundation, SaskWheat, Manitoba Crop Alliance, Alberta Wheat Commission, SaskPulse, Manitoba Canola Growers, Prairie Oat Growers Association, SaskCanola, and Manitoba Pulse and Soybean Growers). The survey was implemented and conducted by Alberta Agriculture and Irrigation, Saskatchewan Ministry of Agriculture, Saskatchewan Crop Insurance Corporation, Manitoba Agriculture, and Agriculture & Agri-Food Canada (AAFC).
Meghan Vankosky, Owen Olfert, Shelley Barkley, James Tansey, Ross Weiss, Jennifer Otani
The risk of wheat midge (Sitodiplosis mosellana) infestation in 2023 was estimated based on the number of non-parasitized wheat midge larval cocoons in soil samples collected during the fall wheat midge survey conducted in 2022 (Figure 6). The forecast based on non-parasitized larvae provides a general picture of existing densities and the potential for damage in 2023. A number of other factors, in addition to parasitism, influence the overwintering and developmental success of larval wheat midge and might affect wheat midge adult emergence and risk of damage to wheat crops in 2023. Weather conditions (especially precipitation levels) in spring 2023, for example, will further influence the extent and timing of wheat midge emergence during the growing season. In spring 2023, the Prairie Pest Monitoring Network will use phenology models and weather conditions to model the expected emergence of wheat midge adults the Weekly Updates.
Wheat midge survey results and forecasts for previous years are shown in Figure 7.
All areas where wheat midge are active during the growing season are susceptible to crop damage because wheat midge larval feeding affects grain yield and quality. Growers in all areas where wheat midge have occurred in the past should monitor their fields during the susceptible crop stage (i.e., emergence of the wheat head from the boot until flowering) and when adult midge are active.
If adult midge density is equal to one midge per four or five wheat heads between emergence of the wheat heads and flowering (anthesis stage), insecticide application may be warranted. Please refer to provincial crop production guides for information about application and registered products. By the anthesis stage insecticides will not be cost effective as any larvae present will have already caused damage. Larvae that hatch from eggs laid late in or after the anthesis stage will not cause significant damage as the more mature wheat kernels are resistant to larval damage. Avoiding insecticide application after the anthesis stage will help protect populations of natural enemies in field crops, including parasitoids of wheat midge, and of other pests. Parasitism by a small parasitoid wasp (Macroglenes penetrans) can keep wheat midge populations from exceeding the economic threshold.
Figure 6. The densities of unparasitized wheat midge (Sitodiplosis mosellana) cocoons in soil samples collected in fall 2022 during the annual wheat midge survey. Risk of wheat midge infestation in 2023 is greatest in regions where wheat midge larval cocoon densities exceeded 600 midge/m2 during the fall 2022 survey, assuming sufficient rainfall in spring of 2023 (map by Ross Weiss, AAFC-Saskatoon).
Figure 7. The densities of unparasitized wheat midge used to forecast risk for the last four growing seasons (maps by David Giffen, AAFC-Saskatoon).
Surveys of wheat midge larval cocoons were conducted by Sharon Nowlan (SK) and by Alberta Agriculture and Irrigation. The survey was funded by Saskatchewan Crop Insurance Corporation, Saskatchewan Wheat Development Commission, and Alberta Agriculture and Irrigation. Prairie Pest Monitoring Network activity related to this survey was funded by the Canadian Agricultural Partnership.
Meghan Vankosky, Owen Olfert, Shelley Barkley, James Tansey, John Gavloski, Ross Weiss, Jennifer Otani
Populations of cabbage seedpod weevil (Ceutorhynchus obstrictus) were quite low north of Calgary in Alberta and Swift Current and Regina in Saskatchewan again in 2022 (Figure 8). In fact, population densities of cabbage seedpod weevil have been declining in Alberta and Saskatchewan over the last few years. In 2022, population densities were the lowest they have been since the first annual surveys were conducted in Alberta (early 2000s) and Saskatchewan (2007). The distribution and densities of cabbage seedpod weevil from 2018-2021 are shown in Figure 9.
No cabbage seedpod weevils were found in sweep samples collected in the Peace River Region of Alberta or British Columbia, but small numbers of weevils have been collected in north-central Alberta that could be source populations for the Peace River region.
In 2022, the greatest population densities were observed in southwestern Saskatchewan, from the AB/SK border to the Swift Current area (Figure 8). Some fields were sampled for cabbage seedpod weevil in Manitoba in 2022. Of those fields, some had weevils present in low numbers, including fields as far east as Carman (Figure 10).
To protect crops from cabbage seedpod weevil damage, monitor canola and brown mustard fields on a regular basis from the bud stage until the end of flowering using the protocol available here. Accurate monitoring requires that sweep samples be collected from multiple locations within a field, with accuracy increasing as the sample size increases. To avoid overestimation of weevil populations, sweep samples should be taken from the interior of the field and not just from field edges. The nominal economic threshold for cabbage seedpod weevil is 2.5 to 4 adult weevils per sweep.
Figure 8. Cabbage seedpod weevil (Ceutorhynchus obstrictus) distribution in Saskatchewan and Alberta based on a sweep net survey conducted in randomly selected Brassica sp. fields in 2022 (map by Ross Weiss, AAFC-Saskatoon).
Figure 9. Density and distribution of cabbage seedpod weevil in 2018-2021 (maps by David Giffen, AAFC-Saskatoon).
Figure 10. Sampling points for the 2022 cabbage seedpod weevil, including fields in Manitoba, Canada, where cabbage seedpod weevils were collected in fields near Carman, MB (map by Ross Weiss, AAFC-Saskatoon).
Surveys were conducted by Alberta Agriculture and Irrigation, Saskatchewan Ministry of Agriculture, Manitoba Agriculture, and Agriculture & Agri-Food Canada (AAFC). This survey is funded through the AgriScience Program as part of the Canadian Agricultural Partnership, a federal, provincial, territorial initiative. Funders include Agriculture & Agri-Food Canada, Western Grains Research Foundation, SaskWheat, Manitoba Crop Alliance, Alberta Wheat Commission, SaskPulse, Manitoba Canola Growers, Prairie Oat Growers Association, SaskCanola, and Manitoba Pulse & Soybean Growers.
Meghan Vankosky, Shelley Barkley, David Giffen, Owen Olfert, Jennifer Otani
Wheat stem sawfly (Cephus cinctus) was surveyed in southern Alberta in 2022 by counting the number of stems cut by wheat stem sawfly larvae along the edges of wheat fields (Figure 11). The 80 fields that were sampled had damage severity levels ranging from very low to high. Many of the fields sampled had at least 2-10% of stems cut (low damage severity); fields in the counties of Vulcan and Forty Mile had fields with high damage severity (>25% of stems cut). Fields in several counties, including Foothills, Willow Creek, Lethbridge, Warner, Wheatland, and Kneehill had 2-25% of stems cut by wheat stem sawfly in 2022, as did some fields around Oyen, Alberta (Figure 11). Although the areas with the highest population densities have shifted slightly between years (Figure 12), sawfly populations continued to increase in 2022 as compared to population densities observed between 2011 and 2017, with some notably high populations found farther north than normal in 2022. At present, wheat stem sawfly populations are not monitored in Saskatchewan. However, in 2022, there were some reports of sawfly damage from several fields across the province, including near Moosejaw, Pense, Biggar, and Cabri, in both spring wheat and durum crops.
Hot and dry weather conditions may contribute to decreased parasitism rates and sawfly population growth. Bracon cephi is the primary parasitoid of wheat stem sawfly. In hot and dry years, wheat plants mature early, limiting B. cephi to one generation and resulting in reduced parasitism rates. In normal growing seasons, B. cephi can have two generations per year and parasitism rates are higher, allowing B. cephi to exert more control over wheat stem sawfly populations. Very wet conditions can also hinder wheat stem sawfly population growth.
Figure 11. Wheat stem sawfly (Cephus cinctus) distribution in Alberta in 2022 based on results of a survey of cut stems in wheat fields counted after harvest (map by David Giffen, AAFC-Saskatoon).
Figure 12. Wheat stem sawfly distribution in Alberta in 2018-2021 (maps by David Giffen, AAFC-Saskatoon).
The survey was coordinated and conducted by Shelley Barkley from Alberta Agriculture and Irrigation and their partners and cooperators.
Meghan Vankosky, James Tansey, Shelley Barkley, John Gavloski, Ross Weiss, Owen Olfert, Jennifer Otani
The pea leaf weevil (Sitona lineatus) is an invasive insect to western Canada. Its primary hosts are field pea and faba bean, which can be damaged by adults feeding on foliage and by larvae feeding on the root nodules. Secondary hosts of pea leaf weevil include alfalfa, clover, and chickpea, but these plants are only affected by adult foliage feeding. The pea leaf weevil was first detected on the prairies near Lethbridge in the late 1990s, in southern Saskatchewan in 2007, and in Manitoba in 2019. Adult pea leaf weevils consume the foliage of field pea and faba bean plants, beginning in the spring, resulting in ‘u’ shaped notches along the margins of the leaves. The survey is conducted annually in the spring when field pea plants range in size between two and six pairs of leaves by counting the number of feeding notches. The number of notches is used to estimate population density, based on the expectation that increasing levels of damage are indicative of increasing population density. The monitoring protocol is available online.
Since becoming established, the range of pea leaf weevil in western Canada has expanded to the east and north. The pea leaf weevil was confirmed in the Peace River Region a few years ago, and evidence of its presence (in low to moderate densities) was observed throughout the region in 2022 (Figure 13). In the rest of Alberta, population densities were greatest in the Edmonton area and north of the Yellowhead Highway (Figure 13). Densities of pea leaf weevil were the quite low in southern Alberta, aside from some fields near the foothills (e.g., counties of Pincher Creek and Cardston), which is quite different from what has been observed in past years (Figure 14).
Pea leaf weevil populations in Saskatchewan were quite low in the western and central agricultural regions in 2022 (Figure 13), similar to observations from the survey in 2019, 2020, and 2021. However, as compared to 2021, more fields in eastern Saskatchewan had moderate to high numbers of notches per plant, with some fields having an average of 9-27 notches per plant (RMs 333, 331, 303, 301, 273 and 271, all northeast of Yorkton).
In Manitoba adult pea leaf weevils were collected and their identity confirmed in 2019. In 2022, pea fields were sampled using the protocol used in Alberta and Saskatchewan. Low to moderate densities of pea leaf weevil, based on foliar damage to peas, were observed in fields in northeast Manitoba in 2022, including fields in the Swan River Valley where pheromone traps were deployed in 2021.
Figure 13. The distribution of pea leaf weevil (Sitona lineatus) in Alberta, Saskatchewan, and Manitoba in 2022, based on a plant damage survey conducted in the spring in randomly selected field pea crops (map by Ross Weiss, AAFC-Saskatoon).
Figure 14. The distribution of pea leaf weevil observed from 2018-2021 (maps by David Giffen, AAFC-Saskatoon).
The pea leaf weevil survey was conducted by Alberta Agriculture and Irrigation, the Saskatchewan Ministry of Agriculture, Manitoba Agriculture, and Agriculture & Agri-Food Canada (AAFC). This survey is funded through the AgriScience Program as part of the Canadian Agricultural Partnership, a federal, provincial, territorial initiative. Funders include AAFC, Western Grains Research Foundation, SaskWheat, Manitoba Crop Alliance, Alberta Wheat Commission, SaskPulse, Manitoba Canola Growers, Prairie Oat Growers Association, SaskCanola, and Manitoba Pulse & Soybean Growers.
Meghan Vankosky, James Tansey, Carter Peru, Shelley Barkley, John Gavloski, Ross Weiss, Owen Olfert, Jennifer Otani
Pheromone-baited traps are used to monitor the arrival of diamondback moth (Plutella xylostella) in spring across western Canada. Diamondback moths have limited ability to survive winter conditions in Canada and re-establish populations each year after migrating from the southern United States and Mexico. Adult diamondback moths were detected in 75% of the traps set up across western Canada in spring of 2022 (Figure 15).
The pheromone trap network is used to determine when adult moths arrive and this information is used for modelling the number of potential generations of diamondback moth that could be possible. Model results are communicated in the Weekly Updates each growing season. Because diamondback moth can develop from the egg to adult stage quite quickly in hot weather, the risk associated with diamondback moth to crucifer crops (including canola), increases as the number of generations increases.
Pheromone traps for diamondback moths cannot be used to determine if diamondback moth populations have reached or surpassed the economic threshold. Rather, they can serve as an early warning that diamondback moths are present and that field scouting during susceptible crop stages is required. A scouting protocol for diamondback moth larvae is available here.
Figure 15. Results of pheromone trapping for diamondback moth in spring 2022 (map by Ross Weiss, AAFC-Saskatoon).
The diamondback moth survey was conducted by Alberta Agriculture and Irrigation, the Saskatchewan Ministry of Agriculture, Manitoba Agriculture, and Agriculture & Agri-Food Canada (AAFC). This survey is funded through the AgriScience Program as part of the Canadian Agricultural Partnership, a federal, provincial, territorial initiative. Funders include AAFC, Western Grains Research Foundation, SaskWheat, Manitoba Crop Alliance, Alberta Wheat Commission, SaskPulse, Manitoba Canola Growers, Prairie Oat Growers Association, SaskCanola, and Manitoba Pulse & Soybean Growers.
The final WEEKLY UPDATE of the 2022 growing season is here!
Thank you to the many people who performed and supported insect pest monitoring in field crops this year! The Prairie Pest Monitoring Network brings together a unique array of incredible cooperators and collaborators at federal, provincial, regional, post-secondary, and industry levels across western Canada! Thanks to these many individuals! The PPMN also thanks our many contributors to the Weekly Updates and Insect of the Week who stand as co-authors at the top of each Post. Last but not least, a small number of key individuals ensure 16 weeks of pertinent content are available through the growing season on behalf of the PPMN – thank you to Ross Weiss, Tamara Rounce, Serge Trudel, Cynthia Schock, Meghan Vankosky, and Jennifer Otani.
Vital insect pest data originates from in-field observations – that’s THE FOUNDATION – and now, more than ever, researchers need support and permission to continue to collect and build the many integral data sets needed to enable improvements in the detection, monitoring, and management of pest risk in field crops grown across the Canadian prairies! Please, this winter, if you’re a producer, connect with a field researcher and give permission for pests to be monitored in your field. If you’re able to monitor, connect with a field researcher to find out how to help. It’s vital that fields ALL ACROSS the prairies represent Canadian agriculture!
This week includes…..
• Weather synopsis • Predicted grasshopper development • Predicted diamondback development • Lygus bug monitoring • Predicted wheat stem sawfly growth • Pre-harvest intervals (PHI) • West nile virus risk • Provincial insect pest report links • Crop report links • Previous posts ….and review the 2022 Insect of the Week lineup – 16 in total!
Questions or problems accessing the contents of this Weekly Update? Please contact us so we can connect you to our information. Past “Weekly Updates” can be accessed on our Weekly Update page.
TEMPERATURE: Though average temperatures for the 2022 growing season continue to be similar to long-term average values, August temperatures have been much warmer than normal. This past week (August 15-21, 2022) the average daily temperature for the prairie region was 1.5 °C warmer than the previous week and almost 5 °C warmer than climate normal temperatures for the region. Last week recorded the warmest weekly average temperature of the 2022 growing season so far. The warmest temperatures were observed across southwestern Saskatchewan and southeastern Alberta (Fig. 1).
Figure 1. Seven-day average temperature (°C) across the Canadian prairies for the period of August 15-21, 2022.
The prairie-wide average 30-day temperature (July 23 – August 21, 2022) was 2 °C warmer than the long-term average value for the same period. Average 30-day temperatures continue to be warmest across southern Alberta and southwestern Saskatchewan (Fig. 2). The average growing season (April 1-August 14, 2022) temperature for the prairies has been similar to climate normal values. The growing season has been coolest in a region extending from Edmonton to the Peace River region (Fig. 3).
Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of July 23 to August 21, 2022.Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to August 21, 2022.
PRECIPITATION: This week (August 15-21, 2022), minimal amounts of rain were reported for Alberta and Saskatchewan. The greatest weekly precipitation amounts occurred across southern Manitoba (Fig. 4). The 30-day (July 23-August 21, 2022) rainfall amounts continue to be greatest across eastern Manitoba while dry conditions persist across the southern and central regions of Alberta and Saskatchewan (Fig. 5). Rainfall amounts across southern Alberta and southwestern Saskatchewan have been 40% less than climate normal values.
Figure 4 Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of August 15-21, 2022.Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies the past 30 days (July 23 to August 21, 2022).
Growing season rainfall for the prairies (April 1 – August 21, 2022) has been near normal for Alberta and above normal across southeastern Saskatchewan and Manitoba. Total rainfall continues to be greatest across Manitoba and eastern Saskatchewan and least across central and south-central Saskatchewan (Fig. 6).
Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to August 21, 2022.
The grasshopper (Acrididae: Melanoplus sanguinipes) model predicts development using biological parameters known for the pest species and environmental data observed across the Canadian prairies on a daily basis. Model outputs provided below as geospatial maps are a tool to help time in-field scouting on a regional scale yet local development can vary and is only accurately assessed through in-field scouting.
Model simulations were used to estimate grasshopper development as of August 21, 2022. Potential risk continues to be greatest across central and southern regions of Saskatchewan and southeastern Alberta. Simulations indicate that prairie populations are in the adult stage and that females are laying eggs in the soil. Since last week, model simulations indicate that oviposition is now occurring across all of the prairies (Fig. 1). Earlier oviposition can result in above-average production of eggs and increased overwintering survival of eggs.
The oviposition index provides a method to assess where egg production is greatest; higher oviposition index values indicate where egg production is greatest. Model runs for the 2022 growing season (April 1 – August 21) predict that oviposition rates have been greatest across a large region that extends from east of Lethbridge to Regina and north to Saskatoon (Fig. 1).
Figure 1. Grasshopper (Melanoplus sanguinipes) oviposition index across the Canadian prairies as of August 21, 2022 . Higher ovipositional index values indicate greater potential for oviposition.
Diamondback moths (DBM; Plutella xylostella) are a migratory invasive species. Each spring adult populations migrate northward to the Canadian prairies on wind currents from infested regions in the southern or western U.S.A. Upon arrival to the prairies, migrant diamondback moths begin to reproduce and this results in subsequent non-migrant populations that may have three or four generations during the growing season.
Recent warm conditions have resulted in the rapid development of diamondback moth populations. Model simulations to August 14, 2022, indicate that the fourth generation of non-migrant adults (based on mid-May arrival dates) are currently occurring across the southern prairies (Fig. 1). DBM development is predicted to be marginally greater in 2022 than expected based on long-term average values (Fig. 2).
Warm conditions during August resulted in rapid development of diamondback moth populations. Model simulations to August 21, 2022, indicate that the fourth generation of non-migrant adults (based on mid-May arrival dates) are currently occurring across most of the prairies (Fig. 1). DBM development is predicted to be marginally greater than long-term average values (Fig. 2).
Figure 1. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of August 21, 2022. Figure 2. Long-term predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of August 21, based on climate normal data.
In-Field Monitoring:Remove plants in an area measuring 0.1 m² (about 12″ square), beat them onto a clean surface and count the number of larvae (Fig. 3) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 3. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.
The economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant). Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).
Figure 4. Diamondback moth pupa within silken cocoon.
On the Canadian prairies, lygus bugs (Heteroptera: Miridae) are normally a complex of several native species usually including Lygus lineolaris, L. keltoni, L. borealis, L. elisus although several more species are distributed throughout Canada. The species of Lygus forming the “complex” can vary by host plant, by region or even seasonally.
Lygus bugs are polyphagous (i.e., feed on plants belonging to several Families of plants) and multivoltine (i.e., capable of producing multiple generations per year). Both the adult (Fig. 1) and five nymphal instar stages (Fig. 2) are a sucking insect that focuses feeding activities on developing buds, pods and seeds. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Recent research in Alberta has resulted in a revision to the thresholds recommended for the management of Lygus in canola. Under ideal growing conditions (i.e., ample moisture) a threshold of 20-30 lygus per 10 sweeps is recommended. Under dry conditions, a lower threshold may be used, however, because drought limits yield potential in canola, growers should be cautious if considering the use of foliar-applied insecticide at lygus densities below the established threshold of 20-30 per 10 sweeps.In drought-affected fields that still support near-average yield potential, a lower threshold of ~20 lygus per 10 sweeps may be appropriate for stressed canola. Even if the current value of canola remains high (e.g., >$19.00 per bu), control at densities of <10 lygus per 10 sweeps is not likely to be economical. Research indicates that lygus numbers below 10 per 10 sweeps (one per sweep) can on occasion increase yield in good growing conditions – likely through plant compensation for a small amount of feeding stress.
Figure 1. Adult Lygus lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Figure 2. Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. In canola, lygus bugs feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind: Begin monitoring canola when it bolts and continues until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20 °C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180 ° sweeps. Count the number of lygus bugs in the net. Sampling becomes more representative IF repeated at multiple spots within a field so sweep in at least 10 locations within a field to estimate the density of lygus bugs.
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page. The Canola Council of Canada’s “Canola Encyclopedia” also summarizes Lygus bugs. The Flax Council of Canada includes Lygus bugs in their Insect Pest downloadable PDF chapter plus the Saskatchewan Pulse Growers summarize Lygus bugs in faba beans.
Warm, dry weather is conducive to wheat stem sawfly (Cephus cinctus) population growth where they are present. Risk of damage to sawfly host crops is greatest when weather conditions are warmer and drier than normal. Risk associated with wheat stem sawfly can be predicted by calculating growth index values, where the growth index describes the potential for wheat stem sawfly population growth. Where growth risk index values are moderate to high, crop damage is more likely than in areas where growth risk index values are low to moderate. Scouting in moderate and high risk areas this fall (especially where wheat stem sawfly populations are known to be present) will provide valuable information about potential crop yield losses this year and about the risk of wheat stem sawfly population damage in next growing season.
Based on growing season weather in 2022 (April 1 to August 22), predicted wheat stem sawfly growth index values are low to moderate across most of the prairies (Fig. 1). This is due to average (in parts of Alberta) to above-average (in parts Manitoba and southeastern Saskatchewan) precipitation during the current growing season. Growth index values, based on 2022 growing season weather are predicted to be greatest in a region that extends from Swift Current to Saskatoon (Fig. 1). This area has been warmer and drier than the rest of the prairies.
Figure 1. Predicted risk for wheat stem sawfly (Cephus cinctus) across the Canadian prairies as of August 21, 2022.
One last time….. The PHI refers to the minimum number of days between a pesticide application and swathing or straight combining of a crop. The PHI recommends sufficient time for a pesticide to break down. PHI values are both crop- and pesticide-specific. Adhering to the PHI is important for a number of health-related reasons but also because Canada’s export customers strictly regulate and test for the presence of trace residues of pesticides.
Here are a few resources to help: • Information about PHI and Maximum Residue Limits (MRL) is available on the Keep It Clean website. • The Pest Management Regulatory Agency has a fact sheet, “Understanding Preharvest Intervals for Pesticides” or download a free PDF copy. • Use Keep It Clean’s “Spray to Swath Interval Calculator” to accurately estimate: ◦ PHI for canola, chickpeas, lentils, faba beans, dry beans, or peas. ◦ How long to wait, if the crop has already been sprayed. ◦ To find a pesticide to suit your timeline. • Access the Pre-Harvest Glyphosate Stage Guide. • And remember Provincial crop protection guides include the PHI for every pesticide x crop combination. The 2022 Crop Production Guides are available as a FREE downloadable PDF for Alberta, Saskatchewan, and Manitoba.
The following is offered to help predict when Culex tarsalis, the vector for West Nile Virus, will begin to fly across the Canadian prairies. This week, regions most advanced in degree-day accumulations for Culex tarsalis are shown in Figure 1 but the unusual heat across the prairies greatly accelerated mosquito development!
As of August 21, 2022and where present, C. tarsalis development has progressed. Remember, areas highlighted yellow have accumulated sufficient heat units for the second generation of C. tarsalis to fly. Many areas of the prairies well exceed the 250-300 DD of base 14.3 °C (e.g., areas orange red any any shade of pink) represented in Figure 1. Outdoor enthusiasts falling within areas highlighted yellow, orange, red or pink should wear DEET to protect against WNV! Historically, southern and central regions of the Canadian prairies are at increased risk for WNV from late July but typically peaks over the long weekend in August.
Figure 1. Predicted development of Culex tarsalis across the Canadian prairies (as of August 21, 2022).
For those following the specifics of the mosquito host-WNV interaction, Figure 2 projects how many days it will take a C. tarsalis female to become fully infective and be able to transmit the virus to another host (bird or human) once the virus is acquired from another bird. This represents the extrinsic incubation period (EIP) of the virus within the mosquito. Figure 2 projects the EIP was approximately 12-14 days in areas highlighted mauve and approximately 22-24 days in areas highlighted light green.
Figure 2. Predicted extrinsic incubation period (EIP) of West Nile Virus within a C. tarsalis female as of August 21, 2022.
The above maps should be compared with historical confirmed cases of WNV. The Public Health Agency of Canada posts information related to West Nile Virus in Canada and also tracks West Nile Virus through human, mosquito, bird and horse surveillance. Link here to access their most current weekly update (reporting date August 13, 2022; retrieved August 26, 2022) and provided below.
Bird surveillance continues to be an important way to detect and monitor West Nile Virus. The Canadian Wildlife Health Cooperative (CWHC) works with governmental agencies (i.e., provincial laboratories and the National Microbiology Laboratory) and other organizations to report the occurrence of WNV. Dead birds retrieved from areas of higher risk of West Nile Virus are tested for the virus. A screenshot of the latest reporting results posted by Canadian Wildlife Health Cooperative is below (retrieved 25Aug2022).
Anyone keen to identify mosquitoes will enjoy this pictorial key for both larvae and adults which is posted on the Centre for Disease Control (CDC) website but sadly lacks a formal citation other than “MOSQUITOES: CHARACTERISTICS OF ANOPHELINES AND CULICINES prepared by Kent S. Littig and Chester J. Stojanovich” and includes Pages 134-150. The proper citation may be Stojanovich, Chester J. & Louisiana Mosquito Control Association. (1982). Mosquito control training manual. pp 152.
Provincial entomologists provide insect pest updates throughout the growing season so link to their information:
MANITOBA’SCrop Pest Updates for 2022 are up and running! Access a PDF copy of the August 24, 2022 issue here. Bookmark their Crop Pest Update Index to readily access these reports and also bookmark their insect pest homepage to access fact sheets and more! • Aphids in soybeans and sunflower, Lygus bugs, grasshoppers, and crickets were described in the August 24 issue.
ALBERTA’SInsect Pest Monitoring Network webpage links to insect survey maps, live feed maps, insect trap set-up videos, and more. There is also a Major Crops Insect webpage. The new webpage does not replace the Insect Pest Monitoring Network page. Remember, AAF’s Agri-News occasionally includes insect-related information. Twitter users can connect to #ABBugChat Wednesdays at 10:00 am.
Questions or problems accessing the contents of this Weekly Update? Please contact us so we can connect you to our information. Past “Weekly Updates” can be accessed on our Weekly Update page.
TEMPERATURE: Average temperatures for the 2022 growing season continue to be similar to long-term average values. This past week (August 8-14, 2022), the average daily temperature for the prairies was 2 °C warmer than the previous week and 2.5 °C warmer than climate normals. The warmest temperatures were observed across southwestern Saskatchewan and the southern and central regions of Alberta (Fig. 1). The prairie-wide average 30-day temperature (July 16 – August 14, 2022) was 1.5 °C warmer than the long-term average 30-day temperature. Average temperatures have been warmest across southern Alberta and southwestern Saskatchewan (Fig. 2).
Figure 1. Seven-day average temperature (°C) across the Canadian prairies for the period of August 8-14, 2022.Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of July 16 to August 14, 2022.
The average growing season (April 1-August 14, 2022) temperature for the prairies has been similar to observed climate normal values. The growing season has been coolest across the Peace River region (Fig. 3).
Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to August 14, 2022.
PRECIPITATION: The greatest weekly precipitation amounts occurred across eastern Saskatchewan last week (August 8-14, 2022) (Fig. 4). 30-day (July 16-August 14, 2022) rainfall amounts continue to be greatest across southeastern Manitoba while dry conditions persist across southern Alberta and southwestern Saskatchewan (Fig. 5).
Figure 4 Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of August 8-14, 2022.Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies the past 30 days (July 16 to August 14, 2022).
Growing season rainfall for the prairies (April 1 – August 14, 2022) has been near normal for Alberta and above normal in Manitoba. Total rainfall continues to be greatest across Manitoba and eastern Saskatchewan and least across central and south-central Saskatchewan (Fig. 6).
Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to August 14, 2022.
The grasshopper (Acrididae: Melanoplus sanguinipes) model predicts development using biological parameters known for the pest species and environmental data observed across the Canadian prairies on a daily basis. Model outputs provided below as geospatial maps are a tool to help time in-field scouting on a regional scale yet local development can vary and is only accurately assessed through in-field scouting.
Model simulations were used to estimate grasshopper development as of August 14, 2022. Potential risk continues to be greatest across central and southern regions of Saskatchewan and southeastern Alberta. Simulations indicate that prairie populations are in the adult stage and females are beginning to lay eggs in the soil. Earlier oviposition can result in above-average production of eggs and increased overwintering survival of eggs.
The oviposition index provides a method to assess where egg production is greatest; higher oviposition index values indicate where egg production is greatest. Model runs for the 2022 growing season (April 1 – August 14) predicted that ovipositon rates so far in 2022 have been greatest across southern Saskatchewan and southeastern Alberta (Fig. 1).
Figure 1. Grasshopper (Melanoplus sanguinipes) oviposition index across the Canadian prairies as of August 14, 2022 . Higher ovipositional index values indicate greater potential for oviposition.
Diamondback moths (DBM; Plutella xylostella) are a migratory invasive species. Each spring adult populations migrate northward to the Canadian prairies on wind currents from infested regions in the southern or western U.S.A. Upon arrival to the prairies, migrant diamondback moths begin to reproduce and this results in subsequent non-migrant populations that may have three or four generations during the growing season.
Recent warm conditions have resulted in the rapid development of diamondback moth populations. Model simulations to August 14, 2022, indicate that the fourth generation of non-migrant adults (based on mid-May arrival dates) are currently occurring across the southern prairies (Fig. 1). DBM development is predicted to be marginally greater in 2022 than expected based on long-term average values (Fig. 2).
Figure 1. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of August 14, 2022. Figure 2. Long-term predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of August 14, based on climate normal data.
In-Field Monitoring:Remove plants in an area measuring 0.1 m² (about 12″ square), beat them onto a clean surface and count the number of larvae (Fig. 2) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 3. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.
The economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant). Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).
Figure 4. Diamondback moth pupa within silken cocoon.
On the Canadian prairies, lygus bugs (Heteroptera: Miridae) are normally a complex of several native species usually including Lygus lineolaris, L. keltoni, L. borealis, L. elisus although several more species are distributed throughout Canada. The species of Lygus forming the “complex” can vary by host plant, by region or even seasonally.
Lygus bugs are polyphagous (i.e., feed on plants belonging to several Families of plants) and multivoltine (i.e., capable of producing multiple generations per year). Both the adult (Fig. 1) and five nymphal instar stages (Fig. 2) are a sucking insect that focuses feeding activities on developing buds, pods and seeds. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Recent research in Alberta has resulted in a revision to the thresholds recommended for the management of Lygus in canola. Under ideal growing conditions (i.e., ample moisture) a threshold of 20-30 lygus per 10 sweeps is recommended. Under dry conditions, a lower threshold may be used, however, because drought limits yield potential in canola, growers should be cautious if considering the use of foliar-applied insecticide at lygus densities below the established threshold of 20-30 per 10 sweeps.In drought-affected fields that still support near-average yield potential, a lower threshold of ~20 lygus per 10 sweeps may be appropriate for stressed canola. Even if the current value of canola remains high (e.g., >$19.00 per bu), control at densities of <10 lygus per 10 sweeps is not likely to be economical. Research indicates that lygus numbers below 10 per 10 sweeps (one per sweep) can on occasion increase yield in good growing conditions – likely through plant compensation for a small amount of feeding stress.
Figure 1. Adult Lygus lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Figure 2. Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. In canola, lygus bugs feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind: Begin monitoring canola when it bolts and continues until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20 °C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180 ° sweeps. Count the number of lygus bugs in the net. Sampling becomes more representative IF repeated at multiple spots within a field so sweep in at least 10 locations within a field to estimate the density of lygus bugs.
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page. The Canola Council of Canada’s “Canola Encyclopedia” also summarizes Lygus bugs. The Flax Council of Canada includes Lygus bugs in their Insect Pest downloadable PDF chapter plus the Saskatchewan Pulse Growers summarize Lygus bugs in faba beans.
The PHI refers to the minimum number of days between a pesticide application and swathing or straight combining of a crop. The PHI recommends sufficient time for a pesticide to break down. PHI values are both crop- and pesticide-specific. Adhering to the PHI is important for a number of health-related reasons but also because Canada’s export customers strictly regulate and test for the presence of trace residues of pesticides.
Here are a few resources to help: • Information about PHI and Maximum Residue Limits (MRL) is available on the Keep It Clean website. • The Pest Management Regulatory Agency has a fact sheet, “Understanding Preharvest Intervals for Pesticides” or download a free PDF copy. • Use Keep It Clean’s “Spray to Swath Interval Calculator” to accurately estimate: ◦ PHI for canola, chickpeas, lentils, faba beans, dry beans, or peas. ◦ How long to wait, if the crop has already been sprayed. ◦ To find a pesticide to suit your timeline. • Access the Pre-Harvest Glyphosate Stage Guide. • And remember Provincial crop protection guides include the PHI for every pesticide x crop combination. The 2022 Crop Production Guides are available as a FREE downloadable PDF for Alberta, Saskatchewan, and Manitoba.
The following is offered to help predict when Culex tarsalis, the vector for West Nile Virus, will begin to fly across the Canadian prairies. This week, regions most advanced in degree-day accumulations for Culex tarsalis are shown in Figure 1 but the unusual heat across the prairies greatly accelerated mosquito development!
As of August 14, 2022and where present, C. tarsalis development has progressed. Remember, areas highlighted yellow have accumulated sufficient heat units for the second generation of C. tarsalis to fly. Many areas of the prairies well exceed the 250-300 DD of base 14.3 °C (e.g., areas orange red any any shade of pink) represented in Figure 1. Outdoor enthusiasts falling within areas highlighted yellow, orange, red or pink should wear DEET to protect against WNV! Historically, southern and central regions of the Canadian prairies are at increased risk for WNV from late July but typically peaks over the long weekend in August.
Figure 1. Predicted development of Culex tarsalis across the Canadian prairies (as of August 14, 2022).
For those following the specifics of the mosquito host-WNV interaction, Figure 2 projects how many days it will take a C. tarsalis female to become fully infective and be able to transmit the virus to another host (bird or human) once the virus is acquired from another bird. This represents the extrinsic incubation period (EIP) of the virus within the mosquito. Figure 2 projects the EIP was approximately 12-15 days in areas highlighted mauve and approximately 22-24 days in areas highlighted light green.
Figure 2. Predicted extrinsic incubation period (EIP) of West Nile Virus within a C. tarsalis female as of August 14, 2022.
The above maps should be compared with historical confirmed cases of WNV. The Public Health Agency of Canada posts information related to West Nile Virus in Canada and also tracks West Nile Virus through human, mosquito, bird and horse surveillance. Link here to access their most current weekly update (reporting date July 30, 2022; retrieved August 18, 2022) and provided below.
Bird surveillance continues to be an important way to detect and monitor West Nile Virus. The Canadian Wildlife Health Cooperative (CWHC) works with governmental agencies (i.e., provincial laboratories and the National Microbiology Laboratory) and other organizations to report the occurrence of WNV. Dead birds retrieved from areas of higher risk of West Nile Virus are tested for the virus. A screenshot of the latest reporting results posted by Canadian Wildlife Health Cooperative is below (retrieved 18Aug2022).
Anyone keen to identify mosquitoes will enjoy this pictorial key for both larvae and adults which is posted on the Centre for Disease Control (CDC) website but sadly lacks a formal citation other than “MOSQUITOES: CHARACTERISTICS OF ANOPHELINES AND CULICINES prepared by Kent S. Littig and Chester J. Stojanovich” and includes Pages 134-150. The proper citation may be Stojanovich, Chester J. & Louisiana Mosquito Control Association. (1982). Mosquito control training manual. pp 152.
Provincial entomologists provide insect pest updates throughout the growing season so link to their information:
MANITOBA’SCrop Pest Updates for 2022 are up and running! Access a PDF copy of the August 17, 2022 issue here. Bookmark their Crop Pest Update Index to readily access these reports and also bookmark their insect pest homepage to access fact sheets and more! • Aphids in soybeans and small grains, Lygus bugs, grasshoppers, crickets, and diamondback moth were described in the August 17 issue.
ALBERTA’SInsect Pest Monitoring Network webpage links to insect survey maps, live feed maps, insect trap set-up videos, and more. There is also a Major Crops Insect webpage. The new webpage does not replace the Insect Pest Monitoring Network page. Remember, AAF’s Agri-News occasionally includes insect-related information. Twitter users can connect to #ABBugChat Wednesdays at 10:00 am.
Questions or problems accessing the contents of this Weekly Update? Please contact us so we can connect you to our information. Past “Weekly Updates” can be accessed on our Weekly Update page.
TEMPERATURE: Average temperatures for the 2022 growing season have been similar to long term average values. This past week (August 1-7, 2022), the average daily temperature across the prairies was 2°C cooler than the previous week and 1°C warmer than the long-term normal (climate normal). The warmest temperatures were observed for the southern prairies (Fig. 1).
Figure 1. Seven-day average temperature (°C) across the Canadian prairies for the period of August 1-7, 2022.
The prairie-wide average 30-day temperature (July 9 – August 7, 2022) was 1.5°C warmer than long-term average values. Average temperatures have been warmest across southeastern Alberta and southwestern Saskatchewan (Fig. 2).
Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of July 9 to August 7, 2022.
The average growing season (April 1 – August 7, 2022) temperature for the prairies has been similar to that expected based on climate normal values. The growing season has been coolest across the Parkland and Peace River regions (Fig. 3).
Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to August 7, 2022.
PRECIPITATION: The lowest weekly (August 1 to 7) precipitation accumulation occurred across southern and central regions of all three prairie provinces (Fig. 4). 30-day (July 9 – August 7, 2022) rainfall amounts have been well below average for northern and western Alberta and near normal across the central and southern regions of Alberta and Saskatchewan (Fig. 5). Precipitation has been above normal in southeastern Saskatchewan and eastern Manitoba.
Figure 4 Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of August 1-7, 2022.Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies the past 30 days (July 9 to August 7, 2022).
Average growing season rainfall for the prairies (April 1 – August 7, 2022) has been approximately 160% of normal. Total rainfall continues to be greatest across Manitoba and eastern Saskatchewan. Cumulative rainfall amounts have been near normal for Saskatchewan and Alberta (Fig. 6).
Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to August 7, 2022.
The grasshopper (Acrididae: Melanoplus sanguinipes) model predicts development using biological parameters known for the pest species and environmental data observed across the Canadian prairies on a daily basis. Model outputs provided below as geospatial maps are a tool to help time in-field scouting on a regional scale yet local development can vary and is only accurately assessed through in-field scouting.
Some areas of the Canadian prairies are presently experiencing high densities of economically important species. Review lifecycle and damage information for this pest to support in-field scouting.
Model simulations were used to estimate grasshopper development as of August 7, 2022. Potential risk continues to be greatest across central and southern regions of Saskatchewan and southeastern Alberta. Adults should now be occurring across central and southern regions of all three prairie provinces. Females are beginning to lay eggs in the soil. Development of grasshopper populations near Moose Jaw, Saskatchewan suggests that local populations are in the adult stage and that oviposition is progressing (Fig. 1). Model output indicates that populations are transitioning to the egg stage (Fig. 2). Potential risk continues to be greatest across the central and southern regions of Saskatchewan.
Figure 1. Predicted development of the migratory grasshopper (Melanoplus sanguinipes) population near Moose Jaw, Saskatchewan as of August 7, 2022.Figure 2. Percentage of the migratory grasshopper (Melanoplus sanguinipes) population expected to be in the egg stage across the Canadian prairies as of August 7, 2022.
Earlier oviposition can result in above average production of eggs and increased overwintering survival of eggs. The oviposition index provides a method to assess where egg production is greatest; higher oviposition index values indicate where egg production is greatest. Model runs for the 2022 growing season (April 1 to August 7, 2022) predict that oviposition rates should be greatest near Winnipeg, Manitoba, Moose Jaw, Saskatchewan and Medicine Hat, Alberta (Fig. 3).
Figure 3. Grasshopper (Melanoplus sanguinipes) oviposition index across the Canadian prairies as of August 7, 2022 . Higher ovipositional index values indicate greater potential for oviposition.
Diamondback moths (DBM; Plutella xylostella) are a migratory invasive species. Each spring adult populations migrate northward to the Canadian prairies on wind currents from infested regions in the southern or western U.S.A. Upon arrival to the prairies, migrant diamondback moths begin to reproduce and this results in subsequent non-migrant populations that may have three or four generations during the growing season.
Model simulations to August 7, 2022, indicate that the third generation of non-migrant adults (based on mid-May arrival dates) are currently occurring across most of the prairies (Fig. 1). DBM development is predicted to be marginally greater in 2022 than expected based on long-term average values (Fig. 2).
Figure 1. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of August 7, 2022. Figure 2. Long-term predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of August 7, based on climate normal data.
Spring Pheromone Trap Monitoring of Adult Males: Across the Canadian prairies, spring monitoring is initiated to acquire weekly counts of adult moths attracted to pheromone-baited delta traps deployed in fields. Weekly trap interceptions are observed to generate cumulative counts. Summaries or maps of cumulative DBM data are available for Manitoba, Saskatchewan and Alberta. These cumulative count estimates are broadly categorized to help producers prioritize and time in-field scouting for larvae.
In-Field Monitoring:Remove plants in an area measuring 0.1 m² (about 12″ square), beat them onto a clean surface and count the number of larvae (Fig. 2) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 3. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.
The economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant). Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).
Figure 4. Diamondback moth pupa within silken cocoon.
On the Canadian prairies, lygus bugs (Heteroptera: Miridae) are normally a complex of several native species usually including Lygus lineolaris, L. keltoni, L. borealis, L. elisus although several more species are distributed throughout Canada. The species of Lygus forming the “complex” can vary by host plant, by region or even seasonally.
Lygus bugs are polyphagous (i.e., feed on plants belonging to several Families of plants) and multivoltine (i.e., capable of producing multiple generations per year). Both the adult (Fig. 1) and five nymphal instar stages (Fig. 2) are a sucking insect that focuses feeding activities on developing buds, pods and seeds. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Recent research in Alberta has resulted in a revision to the thresholds recommended for the management of Lygus in canola. Under ideal growing conditions (i.e., ample moisture) a threshold of 20-30 lygus per 10 sweeps is recommended. Under dry conditions, a lower threshold may be used, however, because drought limits yield potential in canola, growers should be cautious if considering the use of foliar-applied insecticide at lygus densities below the established threshold of 20-30 per 10 sweeps.In drought-affected fields that still support near-average yield potential, a lower threshold of ~20 lygus per 10 sweeps may be appropriate for stressed canola. Even if the current value of canola remains high (e.g., >$19.00 per bu), control at densities of <10 lygus per 10 sweeps is not likely to be economical. Research indicates that lygus numbers below 10 per 10 sweeps (one per sweep) can on occasion increase yield in good growing conditions – likely through plant compensation for a small amount of feeding stress.
Figure 1. Adult Lygus lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Figure 2. Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. In canola, lygus bugs feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind: Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20 °C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180 ° sweeps. Count the number of lygus bugs in the net. Sampling becomes more representative IF repeated at multiple spots within a field so sweep in at least 10 locations within a field to estimate the density of lygus bugs.
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page. The Canola Council of Canada’s “Canola Encyclopedia” also summarizes Lygus bugs. The Flax Council of Canada includes Lygus bugs in their Insect Pest downloadable PDF chapter plus the Saskatchewan Pulse Growers summarize Lygus bugs in faba beans.
Aphid populations can quickly increase at this point in the season and particularly when growing conditions are warm and dry. Over the years, both the Weekly Updates and Insect of the Week included aphid-related information so here’s a list of these items to access when scouting fields:
Remember your pre-harvest intervals. The PHI refers to the minimum number of days between a pesticide application and swathing or straight combining of a crop. The PHI recommends sufficient time for a pesticide to break down. PHI values are both crop- and pesticide-specific. Adhering to the PHI is important for a number of health-related reasons but also because Canada’s export customers strictly regulate and test for the presence of trace residues of pesticides.
Here are a few resources to help: • Information about PHI and Maximum Residue Limits (MRL) is available on the Keep It Clean website. • The Pest Management Regulatory Agency has a fact sheet, “Understanding Preharvest Intervals for Pesticides” or download a free PDF copy. • Use Keeping It Clean’s “Spray to Swath Interval Calculator” to accurately estimate: ◦ PHI for canola, chickpeas, lentils, faba beans, dry beans, or peas. ◦ How long to wait, if the crop’s already been sprayed. ◦ To find a pesticide to suit your timeline. • Access the Pre-Harvest Glyphosate Stage Guide. • And remember Provincial crop protection guides include the PHI for every pesticide x crop combination. The 2022 Crop Production Guides are available as a FREE downloadable PDF for Alberta, Saskatchewan, and Manitoba.
ALBERTA’SInsect Pest Monitoring Network webpage links to insect survey maps, live feed maps, insect trap set-up videos, and more. There is also a Major Crops Insect webpage. The new webpage does not replace the Insect Pest Monitoring Network page. Remember, AAF’s Agri-News occasionally includes insect-related information. Twitter users can connect to #ABBugChat Wednesdays at 10:00 am. • Wheat midge pheromone monitoring update for AB – Cumulative counts arising from weekly data are available on this Live Map. • Cabbage seedpod weevil monitoring update for AB – Cumulative counts arising from weekly data are available on this Live Map. • Bertha armyworm pheromone trap monitoring update for AB – Cumulative counts arising from weekly data are available on this Live Map.
Questions or problems accessing the contents of this Weekly Update? Please contact us so we can connect you to our information. Past “Weekly Updates” can be accessed on our Weekly Update page.
TEMPERATURE: Average temperatures for the 2022 growing season have been similar to long-term average temperature values. This past week (July 25-31, 2022), the average daily temperature on the prairies was 1 °C cooler than the average daily temperature of the previous week and 1.5 °C warmer than the long-term normal temperature. The coolest temperatures were observed across Manitoba and eastern Saskatchewan (Fig. 1).
Figure 1. Seven-day average temperature (°C) across the Canadian prairies for the period of July 25-31, 2022.
The prairie-wide average 30-day temperature (July 2 – July 31, 2022) was 1.5 °C warmer than the long-term average value. Average temperatures have been warmest across a region that extends south from Lethbridge to Saskatoon to Winnipeg (Fig. 2).
Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of July 02 to July 31, 2022.
The average growing season (April 1-July 31, 2022) temperature for the prairies has been similar to climate normal values. The growing season has been coolest across the Parkland and Peace River regions (Fig. 3).
Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to July 31, 2022.
PRECIPITATION: Last week (July 25 to 31), southern Alberta and southwestern Saskatchewan received the lowest amounts of rain of locations across the prairies (Fig. 4). Over the last 30 days (July 2 – July 31, 2022), rainfall amounts have been well below average for northern Alberta and near normal across the central and southern regions of Alberta and Saskatchewan (Fig. 5).
Figure 4 Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of July 25-31, 2022.Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies the past 30 days (July 02 – July 31, 2022).
Precipitation has been above normal in Manitoba. The average growing season rainfall for the prairies (April 1 – July 31, 2022) has been approximately 150% of normal. Total rainfall continues to be greatest across Manitoba and eastern Saskatchewan; cumulative rainfall amounts have been much lower for the central and western regions of Saskatchewan and Alberta. Cumulative rainfall amounts have been near normal for the remainder of Saskatchewan and in Alberta (Fig. 6).
Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to July 31, 2022.
The grasshopper (Acrididae: Melanoplus sanguinipes) model predicts development using biological parameters known for the pest species and environmental data observed across the Canadian prairies on a daily basis. Model outputs provided below as geospatial maps are a tool to help time in-field scouting on a regional scale yet local development can vary and is only accurately assessed through in-field scouting.
Some areas of the Canadian prairies are presently experiencing high densities of economically important species. Review lifecycle and damage information for this pest to support in-field scouting.
Model simulations were used to estimate grasshopper development as of July 31, 2022. Grasshopper development has progressed rapidly over the past few weeks and development rates are more advanced this year than expected based on long-term climate normal values. Based on estimates of average development, populations should consist of 4th (18%) and 5th (37%) instar nymphs and adults (33%) across the southern regions of all three prairie provinces (Fig. 1). Adults should now be occurring across the southern regions of all three prairie provinces (Fig. 1). Model output indicates that oviposition (egg-laying) is now occurring across the southern prairies (Fig. 2). Potential risk continues to be greatest across the central and southern regions of Saskatchewan.
Figure 1. Predicted migratory grasshopper (Melanoplus sanguinipes) development, presented as average instar, across the Canadian prairies as of July 31, 2022.Figure 2. Percent of the migratory grasshopper (Melanoplus sanguinipes) predicted to be in the egg stage across the Canadian prairies as of July 31, 2022.
Diamondback moths (DBM; Plutella xylostella) are a migratory invasive species. Each spring adult populations migrate northward to the Canadian prairies on wind currents from infested regions in the southern or western U.S.A. Upon arrival to the prairies, migrant diamondback moths begin to reproduce and this results in subsequent non-migrant populations that may have three or four generations during the growing season.
Model simulations to July 31, 2022, indicate that the third generation of non-migrant adults (based on mid-May arrival dates) is currently occurring across the southern prairies (Fig. 1). DBM development is predicted to be marginally greater this year than expected based on long-term average values (Fig. 2).
Figure 1. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of July 31, 2022. Figure 2. Long-term predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of July 31, based on climate normal data.
In-Field Monitoring:Remove plants in an area measuring 0.1 m² (about 12″ square), beat them onto a clean surface and count the number of larvae (Fig. 3) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 3. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.
The economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant). Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).
Figure 4. Diamondback moth pupa within silken cocoon.
On the Canadian prairies, lygus bugs (Heteroptera: Miridae) are normally a complex of several native species usually including Lygus lineolaris, L. keltoni, L. borealis, L. elisus although several more species are distributed throughout Canada. The species of Lygus forming the “complex” can vary by host plant, by region or even seasonally.
Lygus bugs are polyphagous (i.e., feed on plants belonging to several Families of plants) and multivoltine (i.e., capable of producing multiple generations per year). Both the adult (Fig. 1) and five nymphal instar stages (Fig. 2) are a sucking insect that focuses feeding activities on developing buds, pods and seeds. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Recent research in Alberta has resulted in a revision to the thresholds recommended for the management of Lygus in canola. Under ideal growing conditions (i.e., ample moisture) a threshold of 20-30 lygus per 10 sweeps is recommended. Under dry conditions, a lower threshold may be used, however, because drought limits yield potential in canola, growers should be cautious if considering the use of foliar-applied insecticide at lygus densities below the established threshold of 20-30 per 10 sweeps.In drought-affected fields that still support near-average yield potential, a lower threshold of ~20 lygus per 10 sweeps may be appropriate for stressed canola. Even if the current value of canola remains high (e.g., >$19.00 per bu), control at densities of <10 lygus per 10 sweeps is not likely to be economical. Research indicates that lygus numbers below 10 per 10 sweeps (one per sweep) can on occasion increase yield in good growing conditions – likely through plant compensation for a small amount of feeding stress.
Figure 1. Adult Lygus lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Figure 2. Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. In canola, lygus bugs feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind: Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20 °C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180 ° sweeps. Count the number of lygus bugs in the net. Sampling becomes more representative IF repeated at multiple spots within a field so sweep in at least 10 locations within a field to estimate the density of lygus bugs.
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page. The Canola Council of Canada’s “Canola Encyclopedia” also summarizes Lygus bugs. The Flax Council of Canada includes Lygus bugs in their Insect Pest downloadable PDF chapter plus the Saskatchewan Pulse Growers summarize Lygus bugs in faba beans.
Aphid populations can quickly increase at this point in the season and particularly when growing conditions are warm and dry. Over the years, both the Weekly Updates and Insect of the Week included aphid-related information so here’s a list of these items to access when scouting fields:
Start to consider pre-harvest intervals. The PHI refers to the minimum number of days between a pesticide application and swathing or straight combining of a crop. The PHI recommends sufficient time for a pesticide to break down. PHI values are both crop- and pesticide-specific. Adhering to the PHI is important for a number of health-related reasons but also because Canada’s export customers strictly regulate and test for the presence of trace residues of pesticides.
Here are a few resources to help: • Information about PHI and Maximum Residue Limits (MRL) is available on the Keep It Clean website. • The Pest Management Regulatory Agency has a fact sheet, “Understanding Preharvest Intervals for Pesticides” or download a free PDF copy. • Use Keeping It Clean’s “Spray to Swath Interval Calculator” to accurately estimate: ◦ PHI for canola, chickpeas, lentils, faba beans, dry beans, or peas. ◦ How long to wait, if the crop’s already been sprayed. ◦ To find a pesticide to suit your timeline. • Access the Pre-Harvest Glyphosate Stage Guide. • And remember Provincial crop protection guides include the PHI for every pesticide x crop combination. The 2022 Crop Production Guides are available as a FREE downloadable PDF for Alberta, Saskatchewan, and Manitoba.
Provincial entomologists provide insect pest updates throughout the growing season so link to their information:
MANITOBA’SCrop Pest Updates for 2022 are up and running! Access the August 3 issue as a PDF on their website. Bookmark their Crop Pest Update Index to readily access these reports and also bookmark their insect pest homepage to access fact sheets and more! • Pests of greatest concern in Manitoba from July 28 to August 3 were armyworms, aphids and grasshoppers. The August 3 update has great information on scouting and monitoring for these pests!
ALBERTA’SInsect Pest Monitoring Network webpage links to insect survey maps, live feed maps, insect trap set-up videos, and more. There is also a Major Crops Insect webpage. The new webpage does not replace the Insect Pest Monitoring Network page. Remember that Agri-News occasionally includes insect-related information. Twitter users can connect to #ABBugChat Wednesdays at 10:00 am MDT.
The following crop reports are also available: • The United States Department of Agriculture (USDA) produces a Crop Progress Report (link to August 1 report on right of the page) • The USDA’s Weekly Weather and Crop Bulletin
Questions or problems accessing the contents of this Weekly Update? Please contact us so we can connect you to our information. Past “Weekly Updates” can be accessed on our Weekly Update page.
TEMPERATURE: Though temperatures over the past 30 days have been warmer than normal, the 2022 growing season across the prairies has been quite similar to that of a ‘normal’ or long-term average season. This past week (July 18-24, 2022), the average daily temperature on the prairies was 2 °C cooler than the average daily temperature of the previous week and 1 °C warmer than the long-term normal temperature. The coolest temperatures were observed across central and northern Alberta (Fig. 1).
Figure 1. Seven-day average temperature (°C) across the Canadian prairies for the period of July 18-24, 2022.
The prairie-wide average 30-day temperature (June 25 – July 24, 2022) was 0.5 °C warmer than the long-term average value. Average temperatures have been warmest across the southern prairies (Fig. 2).
Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of June 25-July 24, 2022.
The average growing season (April 1-July 24, 2022) temperature for the prairies has been 0.2 °C cooler than the climate normal values. The growing season has been warmest across the southern prairies (Fig. 3).
Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to July 24, 2022.
PRECIPITATION: Weekly rainfall accumulation for July 18 to 24 varied across the prairies. Very little precipitation has fallen across the northern prairies (Fig. 4). Observed rainfall amounts across central and northern Alberta were generally less than 5 mm. 30-day (June 25 – July 24, 2022) rainfall amounts have been well below average for the northern prairies and near normal across the southern prairies (Fig. 5).
Figure 4 Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of July 18-24, 2022.Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies the past 30 days (June 25-July 24, 2022).
Growing season rainfall for April 1 – July 24, 2022, continues to be greatest across Manitoba and eastern Saskatchewan; cumulative rainfall amounts have been much lower for the central and western regions of Saskatchewan and Alberta (Fig. 6).
Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to July 24, 2022.
The grasshopper (Acrididae: Melanoplus sanguinipes) model predicts development using biological parameters known for the pest species and environmental data observed across the Canadian prairies on a daily basis. Model outputs provided below as geospatial maps are a tool to help time in-field scouting on a regional scale yet local development can vary and is only accurately assessed through in-field scouting.
Some areas of the Canadian prairies are presently experiencing high densities of economically important species. Review lifecycle and damage information for this pest to support in-field scouting.
Model simulations were used to estimate grasshopper development as of July 24, 2022. As a result of above-normal temperatures, grasshopper development has rapidly progressed over the past few weeks. Last week, adults were just beginning to appear. Based on estimates of average development, populations should consist of 4th (25%) and 5th (34%) instar nymphs and adults (19%) across the southern regions of all three prairie provinces (Fig. 1). Adults should now be occurring across the southern regions of all three prairie provinces (Fig. 2). Potential risk continues to be greatest across the central and southern regions of Saskatchewan.
Figure 1. Predicted migratory grasshopper (Melanoplus sanguinipes) development, presented as average instar, across the Canadian prairies as of July 24, 2022.Figure 2. Long-term average predicted migratory grasshopper (Melanoplus sanguinipes) development, presented as the percent adults, across the Canadian prairies as of July 17, 2022.
Diamondback moths (DBM; Plutella xylostella) are a migratory invasive species. Each spring adult populations migrate northward to the Canadian prairies on wind currents from infested regions in the southern or western U.S.A. Upon arrival to the prairies, migrant diamondback moths begin to reproduce and this results in subsequent non-migrant populations that may have three or four generations during the growing season.
Model simulations to July 24, 2022, indicate that the third generation of non-migrant adults (based on mid-May arrival dates) are currently occurring across the southern prairies (Fig. 1). DBM development is predicted to be marginally greater than long-term average values (Fig. 2).
Figure 1. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of July 24, 2022. Figure 2. Long-term predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of July 24, based on climate normal data.
Spring Pheromone Trap Monitoring of Adult Males: Across the Canadian prairies, spring monitoring is initiated to acquire weekly counts of adult moths attracted to pheromone-baited delta traps deployed in fields. Weekly trap interceptions are observed to generate cumulative counts. Summaries or maps of cumulative DBM data are available for Manitoba, Saskatchewan and Alberta. These cumulative count estimates are broadly categorized to help producers prioritize and time in-field scouting for larvae.
In-Field Monitoring:Remove plants in an area measuring 0.1 m² (about 12″ square), beat them onto a clean surface and count the number of larvae (Fig. 2) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 2. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.
The economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant). Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).
Figure 3. Diamondback moth pupa within silken cocoon.
The following maps represent predicted regional estimates of wheat midge development. Remember – field level populations are assessed only through in-field scouting.
As of July 24, 2022, where wheat midge is present, model simulations predict that Albertan populations should be primarily in the egg stage, while populations across Manitoba and eastern Saskatchewan should consist of larvae developing in wheat heads (Fig. 1).
Figure 1. Wheat midge larvae (AAFC)
Regional differences in wheat midge development can be attributed to rainfall differences that occurred in May and June. Optimal rainfall in May and June across Saskatchewan and Manitoba has resulted in faster rates of wheat midge development rates than in Alberta. As a result, some adult wheat midge may still be active in Alberta (Fig. 2), while adult populations should have peaked and should be declining across Saskatchewan and Manitoba. Populations in the Peace River region are predicted to be primarily in the egg stage (Fig. 3). Across Manitoba and Saskatchewan, populations are predicted to be transitioning from the egg stage to the larval stage (Fig. 4). Wheat midge developmental rates near Regina, Saskatchewan are predicted to be greater than for Grande Prairie, Alberta.
Figure 2. Percent of wheat midge larval population (Sitodiplosis mosellana) that is in the adult stage, across western Canada,as of July 24, 2022.Figure. 3. Percent of wheat midge population (Sitodiplosis mosellana) that is in the egg stage across western Canada, as of July 24, 2022.Figure 4. Percent of wheat midge population (Sitodiplosis mosellana) that is in the larval stage (in wheat heads), across western Canada, as of July 24, 2022.
Model simulations indicate that egg development is complete and populations are primarily in the larval stage (>90%) for populations near Regina (Fig. 5) while Grande Prairie populations are predicted be in both egg (31%) and larval stages (61%) (Fig. 6). Potential risk continues to be greatest across eastern Saskatchewan and Manitoba.
Figure 5. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Regina, Saskatchewanas of July 24, 2022. Figure 6. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Grande Prairie, Alberta,as of July 24, 2022.
In-Field Monitoring:The window for scouting and application of the economic threshold for wheat midge (i.e., during the synchrony between wheat anthesis and midge flight period) has now drawn to a close for 2022.
Additional information can be accessed by reviewing the Wheat midge pages extracted from the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page.
Aphid populations can quickly increase at this point in the season and particularly when growing conditions are warm and dry. Over the years, both the Weekly Updates and Insect of the Week included aphid-related information so here’s a list of these items to access when scouting fields:
On the Canadian prairies, lygus bugs (Heteroptera: Miridae) are normally a complex of several native species usually including Lygus lineolaris, L. keltoni, L. borealis, L. elisus although several more species are distributed throughout Canada. The species of Lygus forming the “complex” can vary by host plant, by region or even seasonally.
Lygus bugs are polyphagous (i.e., feed on plants belonging to several Families of plants) and multivoltine (i.e., capable of producing multiple generations per year). Both the adult (Fig. 1) and five nymphal instar stages (Fig. 2) are a sucking insect that focuses feeding activities on developing buds, pods and seeds. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Recent research in Alberta has resulted in a revision to the thresholds recommended for the management of Lygus in canola. Under ideal growing conditions (i.e., ample moisture) a threshold of 20-30 lygus per 10 sweeps is recommended. Under dry conditions, a lower threshold may be used, however, because drought limits yield potential in canola, growers should be cautious if considering the use of foliar-applied insecticide at lygus densities below the established threshold of 20-30 per 10 sweeps.In drought-affected fields that still support near-average yield potential, a lower threshold of ~20 lygus per 10 sweeps may be appropriate for stressed canola. Even if the current value of canola remains high (e.g., >$19.00 per bu), control at densities of <10 lygus per 10 sweeps is not likely to be economical. Research indicates that lygus numbers below 10 per 10 sweeps (one per sweep) can on occasion increase yield in good growing conditions – likely through plant compensation for a small amount of feeding stress.
Figure 1. Adult Lygus lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Figure 2. Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. In canola, lygus bugs feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind: Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20 °C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180 ° sweeps. Count the number of lygus bugs in the net. Sampling becomes more representative IF repeated at multiple spots within a field so sweep in at least 10 locations within a field to estimate the density of lygus bugs.
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page. The Canola Council of Canada’s “Canola Encyclopedia” also summarizes Lygus bugs. The Flax Council of Canada includes Lygus bugs in their Insect Pest downloadable PDF chapter plus the Saskatchewan Pulse Growers summarize Lygus bugs in faba beans.
There is one generation of cabbage seedpod weevil (CSPW; Ceutorhynchus obstrictus) per year. The overwintered adult is an ash-grey weevil measuring 3-4mm long (e.g., lower left photo). Mating and oviposition are quickly followed by eggs hatching within developing canola pods (e.g., lower right photo). The highly concealed larvae feed within the pod, consuming the developing seeds.
Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss. Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo). Eggs are oval and an opaque white, each measuring ~1mm long. Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod.
There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo). The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds. A single larva consumes about 5 canola seeds. The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell. Approximately 10 days later, the new adult emerges to feed on maturing canola pods. Later in the season, these new adults migrate to overwintering sites beyond the field.
Monitoring:
Begin sampling when the crop first enters the bud stage and continue through the flowering.
Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location.
Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field.
Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur.
An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts).
Consider making insecticide applications late in the day to reduce the impact on pollinators. Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators.
High numbers of adults in the fall may indicate the potential for economic infestations the following spring.
Albertan growers can report and check the live map for CSPW posted by Alberta Agriculture and Forestry (screenshot provided below for reference; retrieved 2022Jul28).
The pea leaf weevil is a slender greyish-brown insect measuring approximately 5 mm in length (Fig. 1, Left image). Pea leaf weevil resembles the sweet clover weevil (Sitona cylindricollis) but the former is distinguished by three light-coloured stripes extending length-wise down thorax and sometimes the abdomen. All species of Sitona, including the pea leaf weevil, have a short snout.
Figure 1. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (AAFC-Otani).
Adults will feed upon the leaf margins and growing points of legume seedlings (alfalfa, clover, dry beans, faba beans, peas) and produce a characteristic, scalloped (notched) edge (Fig. 2). Females lay their eggs in the soil either near or on developing pea or faba bean plants from May to June.
Figure 2. Examples of adult pea leaf weevil damage on field pea seedlings, (A) seedling with notches on all nodes, (B) stereotypical crescent shaped notches on the leaf margin, (C) clam or terminal leaf of the pea seedling with arrows indicating the feeding notches. All photos courtesy of Dr. L. Dosdall.
Larvae develop under the soil and are “C” shaped and milky-white with a dark-brown head capsule ranging in length from 3.5-5.5 mm (Figure 3). Larvae develop through five instar stages. After hatching, larvae seek and enter the roots of a pea plant. Larvae will enter and consume the contents of the nodules of the legume host plant. It is the nodules that are responsible for nitrogen-fixation which affect yield plus the plant’s ability to input nitrogen into the soil. Consumption of or damage to the nodules (Figure 4) results in partial or complete inhibition of nitrogen fixation by the plant and results in poor plant growth and low seed yields.
Figure 3. Larva of pea leaf weevil in soil (Photo: L. Dosdall).Figure 4. Damaged pea nodules (Photo: L. Dosdall).
The following is offered to help predict when Culex tarsalis, the vector for West Nile Virus, will begin to fly across the Canadian prairies. This week, regions most advanced in degree-day accumulations for Culex tarsalis are shown in Figure 1 but the unusual heat across the prairies greatly accelerated mosquito development!
As of July 24, 2022, C. tarsalis development is now on the verge of the second generation of adults beginning to fly in areas highlighted yellow (i.e., 250-300 DD of base 14.3 °C) represented below in Figure 1. Outdoor enthusiasts falling within areas highlighted orange or yellow should begin to wear DEET to protect against WNV! Historically, southern and central regions of the Canadian prairies are now in a period of increased risk for WNV that typically peaks over the long weekend in August.
Figure 1. Predicted development of Culex tarsalis across the Canadian prairies (as of July 24, 2022).
For those following the specifics of the mosquito host-WNV interaction, Figure 2 projects how many days it will take a C. tarsalis female to become fully infective and be able to transmit the virus to another host (bird or human) once the virus is acquired from another bird. This represents the extrinsic incubation period (EIP) of the virus within the mosquito. Figure 2 projects the EIP is approximately 17 days in areas highlighted red and approximately 15 days in areas highlighted pink.
Figure 2. Predicted extrinsic incubation period (EIP) of West Nile Virus within a C. tarsalis female as of July 24, 2022.
The above maps should be compared with historical confirmed cases of WNV. The Public Health Agency of Canada posts information related to West Nile Virus in Canada and also tracks West Nile Virus through human, mosquito, bird and horse surveillance. Link here to access their most current weekly update (reporting date November 18, 2021; retrieved July 28, 2022). The screenshot below (retrieved 28Jul2022) serves as a background reference of what was reported in 2021.
Bird surveillance continues to be an important way to detect and monitor West Nile Virus. The Canadian Wildlife Health Cooperative (CWHC) works with governmental agencies (i.e., provincial laboratories and the National Microbiology Laboratory) and other organizations to report the occurrence of WNV. Dead birds retrieved from areas of higher risk of West Nile Virus are tested for the virus. A screenshot of the latest reporting results posted by Canadian Wildlife Health Cooperative is below (retrieved 28Jul2022).
Anyone keen to identify mosquitoes will enjoy this pictorial key for both larvae and adults which is posted on the Centre for Disease Control (CDC) website but sadly lacks a formal citation other than “MOSQUITOES: CHARACTERISTICS OF ANOPHELINES AND CULICINES prepared by Kent S. Littig and Chester J. Stojanovich” and includes Pages 134-150. The proper citation may be Stojanovich, Chester J. & Louisiana Mosquito Control Association. (1982). Mosquito control training manual. pp 152.
Prompted by recent discussions at Results Driven Agriculture Research (RDAR) meetings, a survey has been initiated as part of an M.Sc. research project in the Faculty of Science at the University of Alberta to assess the effectiveness and producer preferences for entomological extension in agriculture in Alberta. The project is funded by RDAR and the Alberta Pulse Growers.
Start to consider pre-harvest intervals. The PHI refers to the minimum number of days between a pesticide application and swathing or straight combining of a crop. The PHI recommends sufficient time for a pesticide to break down. PHI values are both crop- and pesticide-specific. Adhering to the PHI is important for a number of health-related reasons but also because Canada’s export customers strictly regulate and test for the presence of trace residues of pesticides.
Here are a few resources to help: • Information about PHI and Maximum Residue Limits (MRL) is available on the Keep It Clean website. • The Pest Management Regulatory Agency has a fact sheet, “Understanding Preharvest Intervals for Pesticides” or download a free PDF copy. • Use Keeping It Clean’s “Spray to Swath Interval Calculator” to accurately estimate: ◦ PHI for canola, chickpeas, lentils, faba beans, dry beans, or peas. ◦ How long to wait, if the crop’s already been sprayed. ◦ To find a pesticide to suit your timeline. • Access the Pre-Harvest Glyphosate Stage Guide. • And remember Provincial crop protection guides include the PHI for every pesticide x crop combination. The 2022 Crop Production Guides are available as a FREE downloadable PDF for Alberta, Saskatchewan, and Manitoba.
Provincial entomologists provide insect pest updates throughout the growing season so link to their information:
MANITOBA’SCrop Pest Updates for 2022 are up and running! Access a PDF copy of the July 27, 2022 issue here. Bookmark their Crop Pest Update Index to readily access these reports and also bookmark their insect pest homepage to access fact sheets and more! • Pea aphids, aphids in small grains, grasshoppers and armyworm larvae in MB were emphasized in the July 27 issue. • Bertha armyworm pheromone trap monitoring is underway in MB – Review this summary (as of July 26, 2022) of cumulative weekly counts. • Armyworm pheromone trap monitoring is underway in MB – Review this summary (as of July 12, 2022) of counts compiled from Manitoba, Eastern Canada and several northeast states of the United States.
ALBERTA’SInsect Pest Monitoring Network webpage links to insect survey maps, live feed maps, insect trap set-up videos, and more. There is also a Major Crops Insect webpage. The new webpage does not replace the Insect Pest Monitoring Network page. Remember, AAF’s Agri-News occasionally includes insect-related information. Twitter users can connect to #ABBugChat Wednesdays at 10:00 am. • Wheat midge pheromone monitoring update for AB – Cumulative counts arising from weekly data are available on this Live Map. • Cabbage seedpod weevil monitoring update for AB – Cumulative counts arising from weekly data are available on this Live Map. • Bertha armyworm pheromone trap monitoring update for AB – Cumulative counts arising from weekly data are available on this Live Map.
Questions or problems accessing the contents of this Weekly Update? Please contact us so we can connect you to our information. Past “Weekly Updates” can be accessed on our Weekly Update page.
TEMPERATURE: Though recent temperatures have been warmer than normal, the 2022 growing season across the prairies continues to be marginally cooler than average. This past week (July 11-17, 2022) the average daily temperature (prairies) was 2.5 °C warmer than last week. Coolest temperatures were observed across Alberta (Fig. 1). The prairie-wide average 30-day temperature (June 18 – July 17, 2022) was 1.5 °C warmer than the long-term average value. Average temperatures have been warmest across the southern prairies, particularly across Saskatchewan and Manitoba (Fig. 2).
Figure 1. Seven-day average temperature (°C) across the Canadian prairies for the period of July 11-17, 2022.Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of June 18-July 17, 2022.
The average growing season (April 1-July 17, 2022) temperature for the prairies has been 0.3 °C cooler than climate normal values. The growing season has been warmest across the southern prairies (Fig. 3).
Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to July 17, 2022.
PRECIPITATION: Weekly (July 11-17, 2022) rainfall varied across the prairies. Highest rainfall amounts were reported across southern Manitoba and southeastern Saskatchewan (Fig. 4). Observed rainfall events across Alberta were generally less than 5 mm. The 30-day (June 18 – July 17, 2022) rainfall amounts have been well below average for the Peace River region, average to above average for Alberta, below normal for Saskatchewan and near normal to above normal across Manitoba (Fig. 5).
Figure 4 Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of July 11-17, 2022.Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies the past 30 days (June 18-July 17, 2022).
Growing season rainfall for April 1 – July 17, 2022, continues to be greatest across Manitoba and eastern Saskatchewan; cumulative rainfall amounts have been much lower for central and western regions of Saskatchewan and Alberta (Fig. 6).
Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to July 17, 2022.
The following maps represent predicted regional estimates of wheat midge development. Remember – the rate of development and density varies at the field level and can only be verified through in-field scouting. Midge flight coinciding with the beginning of anthesis is a crucial point when in-field counts of adults on plants are carefully compared to the economic thresholds!
As of July 17, 2022, where wheat midge are present, model simulations predict that eggs and larvae (in heads) are the two prevalent stages occurring across the prairies. Differences in wheat midge development are attributed to rainfall differences across the prairies. Optimal rain events in May and June across Saskatchewan and Manitoba have contributed towards and advanced development rates of WM populations whereas populations in southern and central Alberta remain largely in the adult stage (Fig. 1). Adult populations in Saskatchewan and Manitoba are predicted to have peaked and are declining. Populations in the Peace River region are predicted to be primarily in the egg stage (Fig. 2). Across Manitoba and Saskatchewan, populations are predicted to be transitioning from the egg stage to the larval stage (Fig. 3).
Figure 1. Percent of wheat midge larval population (Sitodiplosis mosellana) that is in the pupal stage, across western Canada,as of July 17, 2022.Figure. 2. Percent of wheat midge population (Sitodiplosis mosellana) that is in the egg stage across western Canada, as of July 17, 2022.Figure 3. Percent of wheat midge population (Sitodiplosis mosellana) that is in the larval stage (in wheat heads), across western Canada, as of July 17, 2022.
Wheat midge development can be very site specific. For example, (as of July 17, 2022) developmental rates near Regina, Saskatchewan were predicted to be greater than for Yorkton, Saskatchewan, and Grande Prairie, Alberta. Model simulations indicate that populations near Regina were predominantly in the larval stage (Fig. 4) while Yorkton and Grande Prairie populations were predicted to be predominantly eggs (Figs. 5 and 6).
Figure 4. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Regina, Saskatchewanas of July 17, 2022.Figure 5. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Yorkton, Saskatchewanas of July 17, 2022. Figure 6. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Grande Prairie, Alberta,as of July 17, 2022.
In-Field Monitoring:When scouting wheat fields, pay attention to the synchrony between flying midge and anthesis.
In-field monitoring for wheat midge should be carried out in the evening (preferably after 8:30 pm or later) when the female midges are most active. On warm (at least 15 ºC), calm evenings, the midge can be observed in the field, laying their eggs on the wheat heads (Fig. 5). Midge populations can be estimated by counting the number of adults present on 4 or 5 wheat heads. Inspect the field daily in at least 3 or 4 locations during the evening.
Figure 5. Wheat midge (Sitodiplosis mosellana) laying their eggs on a wheat head. Photo: AAFC-Beav-S. Dufton and A. Jorgensen.
REMEMBER that in-field counts of wheat midge per head remain the basis of the economic threshold decision. Also remember that the parasitoid, Macroglenes penetrans (Fig. 6), is actively searching for wheat midge at the same time. Preserve this parasitoid whenever possible and remember insecticide control options for wheat midge also kill these beneficial insects who help reduce midge populations.
Figure 6. Macroglenes penetrans, a parasitoid wasp that attacks wheat midge, measures only ~2 mm long. Photo: AAFC-Beav-S. Dufton.
Economic Thresholds for Wheat Midge: a) To maintain optimum No. 1 grade: 1 adult midge per 8 to 10 wheat heads during the susceptible stage. b) To maintain yield only: 1 adult midge per 4 to 5 heads. At this level of infestation, wheat yields will be reduced by approximately 15% if the midge is not controlled. Inspect the developing kernels for the presence of larvae and larval damage.
Wheat midge was featured as the Insect of the Week in 2021 (for Wk07). Be sure to also review wheat midge and its doppelganger, the lauxanid fly, featured as the Insect of the Week in 2019 (for Wk11) – find descriptions and photos to help with in-field scouting! Additionally, the differences between midges and parasitoid wasps were featured as the Insect of the Week in 2019 (for Wk12). Remember – not all flying insects are mosquitoes nor are they pests! Many are important parasitoid wasps that actually regulate insect pest species in our field crops OR pollinators that perform valuable ecosystem services!
Additional information can be accessed by reviewing the Wheat midge pages extracted from the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page.
The grasshopper (Acrididae: Melanoplus sanguinipes) model predicts development using biological parameters known for the pest species and environmental data observed across the Canadian prairies on a daily basis. Model outputs provided below as geospatial maps are a tool to help time in-field scouting on a regional scale but local development can vary and is only accurately assessed through in-field scouting.
SCOUT NOW – Some areas of the Canadian prairies are presently experiencing high densities of economically important species. Review lifecycle and damage information for this pest to support in-field scouting.
Model simulations were used to estimate grasshopper development as of July 17, 2022. Based on estimates of average nymphal development, populations should consist of primarily in the 4th and 5th instar and adults across southern regions of all three prairie provinces (Fig. 1). Adults should now be occurring across southern regions of all three prairie provinces (Fig. 2).
Figure 1. Predicted migratory grasshopper (Melanoplus sanguinipes) development, presented as average instar, across the Canadian prairies as of July 17, 2022.Figure 2. Long-term average predicted migratory grasshopper (Melanoplus sanguinipes) development, presented as the percent adults, across the Canadian prairies as of July 17, based on climate normal data.
Diamondback moths (DBM; Plutella xylostella) are a migratory invasive species. Each spring adult populations migrate northward to the Canadian prairies on wind currents from infested regions in the southern or western U.S.A. Upon arrival to the prairies, migrant diamondback moths begin to reproduce and this results in subsequent non-migrant populations that may have three or four generations during the growing season.
Model simulations to July 17, 2022, indicate that the second generation of non-migrant adults (based on mid-May arrival dates) are currently occurring across the Canadian prairies (Fig. 1). This week, development of the second generation has expanded across most of the Peace River region and the third generation is predicted to occur in a localized region of southern Manitoba. DBM development is predicted to be similar to average values (Fig. 2).
Figure 1. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of July 17, 2022. Figure 2. Long-term predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of July 17, based on climate normal data.
Spring Pheromone Trap Monitoring of Adult Males: Across the Canadian prairies, spring monitoring is initiated to acquire weekly counts of adult moths attracted to pheromone-baited delta traps deployed in fields. Weekly trap interceptions are observed to generate cumulative counts. Summaries or maps of cumulative DBM data are available for Manitoba, Saskatchewan and Alberta. These cumulative count estimates are broadly categorized to help producers prioritize and time in-field scouting for larvae.
In-Field Monitoring:Remove plants in an area measuring 0.1 m² (about 12″ square), beat them onto a clean surface and count the number of larvae (Fig. 2) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 2. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.
The economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant). Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).
Figure 3. Diamondback moth pupa within silken cocoon.
The following is offered to help predict when Culex tarsalis, the vector for West Nile Virus, will begin to fly across the Canadian prairies. This week, regions most advanced in degree-day accumulations for Culex tarsalis are shown in Figure 1 but the unusual heat across the prairies greatly accelerated mosquito development!
As of July 17, 2022, C. tarsalis development is now on the verge of the second generation of adults beginning to fly in areas highlighted yellow (i.e., 250-300 DD of base 14.3 °C) represented below in Figure 1. Outdoor enthusiasts falling within areas highlighted orange or yellow should begin to wear DEET to protect against WNV! Historically, southern and central regions of the Canadian prairies are now entering a period of increased risk for WNV that typically peaks over the long weekend in August.
Figure 1. Predicted development of Culex tarsalis across the Canadian prairies (as of July 17, 2022).
For those following the specifics of the mosquito host-WNV interaction, Figure 2 projects how many days it will take a C. tarsalis female to become fully infective and be able to transmit the virus to another host (bird or human) once the virus is acquired from another bird. This represents the extrinsic incubation period (EIP) of the virus within the mosquito. Figure 2 projects the EIP is approximately 14 days in areas highlighted red.
Figure 2. Predicted extrinsic incubation period (EIP) of West Nile Virus within a C. tarsalis female as of July 17, 2022.
The above maps should be compared with historical confirmed cases of WNV. The Public Health Agency of Canada posts information related to West Nile Virus in Canada and also tracks West Nile Virus through human, mosquito, bird and horse surveillance. Link here to access their most current weekly update (reporting date November 18, 2021; retrieved July 20, 2022). The screenshot below (retrieved 20Jul2022) serves as a background reference of what was reported in 2021.
Bird surveillance continues to be an important way to detect and monitor West Nile Virus. The Canadian Wildlife Health Cooperative (CWHC) works with governmental agencies (i.e., provincial laboratories and the National Microbiology Laboratory) and other organizations to report the occurrence of WNV. Dead birds retrieved from areas of higher risk of West Nile Virus are tested for the virus. A screenshot of the latest reporting results posted by Canadian Wildlife Health Cooperative is below (retrieved 20Jul2022).
Anyone keen to identify mosquitoes will enjoy this pictorial key for both larvae and adults which is posted on the Centre for Disease Control (CDC) website but sadly lacks a formal citation other than “MOSQUITOES: CHARACTERISTICS OF ANOPHELINES AND CULICINES prepared by Kent S. Littig and Chester J. Stojanovich” and includes Pages 134-150. The proper citation may be Stojanovich, Chester J. & Louisiana Mosquito Control Association. (1982). Mosquito control training manual. pp 152.
Start to consider pre-harvest intervals. The PHI refers to the minimum number of days between a pesticide application and swathing or straight combining of a crop. The PHI recommends sufficient time for a pesticide to break down. PHI values are both crop- and pesticide-specific. Adhering to the PHI is important for a number of health-related reasons but also because Canada’s export customers strictly regulate and test for the presence of trace residues of pesticides.
Here are a few resources to help: • Information about PHI and Maximum Residue Limits (MRL) is available on the Keep It Clean website. • The Pest Management Regulatory Agency has a fact sheet, “Understanding Preharvest Intervals for Pesticides” or download a free PDF copy. • Use Keeping It Clean’s “Spray to Swath Interval Calculator” to accurately estimate: ◦ PHI for canola, chickpeas, lentils, faba beans, dry beans, or peas. ◦ How long to wait, if the crop’s already been sprayed. ◦ To find a pesticide to suit your timeline. • Access the Pre-Harvest Glyphosate Stage Guide. • And remember Provincial crop protection guides include the PHI for every pesticide x crop combination. The 2022 Crop Production Guides are available as a FREE downloadable PDF for Alberta, Saskatchewan, and Manitoba.
