Week 7 and things are about to get really busy for in-field scouting! Be sure to catch the Insect of the Week – it’s wheat midge! This week find updates to predictive model outputs for grasshoppers, wheat midge, bertha armyworm, cereal leaf beetle, alfalfa weevil, and diamondback moth plus a lot more to help prepare for in-field scouting!
Stay safe and good scouting to you!
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: This past week (June 7-13, 2021), weekly temperatures were above normal and rainfall in eastern Saskatchewan and Manitoba were above normal. The warmest temperatures were observed across Manitoba and Saskatchewan (Fig. 1). Across the prairies, the average 30-day (May 15 – June 13) temperature was 1 °C warmer than climate normal values. Warmest temperatures were observed across southern Manitoba (Fig. 2). The 2021 growing season (April 1 – June 13, 2021) has been characterized by near normal temperatures (Fig. 3).
PRECIPITATION: This week, the highest rainfall amounts were reported across eastern Saskatchewan and most of Manitoba. Minimal rainfall was reported across most of Alberta (Fig. 4). Rainfall amounts for the period of May 15-June 13 (30-day accumulation) were above normal (150% of long-term average values). Rainfall amounts have been above normal for northeastern Alberta, northwestern and southeastern Saskatchewan, and western Manitoba. Well above normal rain was reported for Lloydminster, Regina, and Brandon regions. Below normal rainfall amounts were reported for the Peace River region and southern Alberta (Fig. 5). Average growing season (April 1 – June 13) precipitation was 116% of normal with the greatest precipitation occurring across eastern Saskatchewan, including Regina and an area extending from Brandon to Winnipeg. Below normal rainfall has been reported across western Saskatchewan and southern Alberta (Fig. 6).
Access background information for how and why wind trajectories are monitored in this post.
1. REVERSE TRAJECTORIES (RT) Similar to last week, this week there were an increasing number of reverse trajectories moving north from the Pacific Northwest (Idaho, Oregon and Washington) (Fig. 1). Though this US region can be a source of diamondback moths (DBM), the ECCC models predict air movement, not actual occurrence of diamondback moths. Fields (and DBM traps) should be monitored for DBM adults and larvae.
a. Pacific Northwest (Idaho, Oregon, Washington) – This week (June 11-15, 2021) there were 109 trajectories (versus 106 last week) that crossed Alberta, Manitoba and Saskatchewan (Fig. 2).
b. Mexico and southwest USA (Texas, California) – Compared to previous years, there has been a noticeable increase in number of trajectories from the southern US. The majority of these trajectories have crossed Manitoba and eastern Saskatchewan (Fig. 3). This week (June 11-15, 2021) there have been 11 trajectories (10 last week) that originated in Mexico or the southwest USA that have crossed the prairies.
c. Oklahoma and Texas – The majority of these trajectories passed over Manitoba and eastern Saskatchewan (Fig. 4). This week (June 11-15, 2021) there were 18 trajectories (13 last week) originating in Oklahoma or Texas that passed over the prairies.
d. Kansas and Nebraska – This week (June 11-15, 2021) there were 20 trajectories (19 last week) that originated in Kansas or Nebraska that passed over the prairies (Fig. 5).
2. FORWARD TRAJECTORIES (FT) a. This week there was a decrease in the number of forward trajectories predicted to cross the prairies (Fig. 6). The dates on the graph report when the trajectories originated in the USA (blue bars). These trajectories generally require 3-5 days to enter the prairies (red line). The data suggests that there will be increased potential for introduction of DBM to the prairies.
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 June 13, 2021 (using a biofix date of May 15, 2021), indicate that the first generation of non-migrant adults are currently emerging across the Canadian prairies (Fig. 1).
So far, Manitoba, Saskatchewan, Alberta and the BC Peace are all reporting relatively low numbers of intercepted DBM in pheromone traps (read provincial insect pest report links) despite the fact that favourable wind trajectories have passed over the Canadian prairies from southern regions of North America (review wind trajectory reports for 2021). Even so, once DBM are present in an area, it is important to monitor individual canola fields for larvae. Warm growing conditions can quickly translate into multiple generations in a very short time so use the following photos to help identify larvae (Fig. 2), pupae (Fig. 3), or adults (Fig. 4)!
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.
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).
Model simulations were used to estimate grasshopper (Melanoplus sanguinipes) development as of June 13, 2021. Average development of eggs is 90 % and well ahead of the long-term average of 80 %. As of June 13, the hatch is predicted to be underway across most of the prairies with a prairie average of 45 % (versus 26 % last week). Hatch rates were greater than 75 % across southern Manitoba, Saskatchewan and Alberta. Development in central and Peace River regions of Alberta has been significantly slower than the rest of the prairies (Fig. 1).
Development of grasshopper nymphs, based on average instar, is greatest across Manitoba (Fig. 2). Above normal temperatures have resulted in the rapid development of grasshopper populations across Manitoba and Saskatchewan. Grasshopper populations south of Winnipeg are predicted to be mostly in the 3rd and 4th instar stages. Nymph development, as of June 13, 2021, is greater than long-term average values across most of the prairies (Fig. 3).
The model was projected to June 29 to determine potential development at Saskatoon and Winnipeg over the next two weeks. Results suggest that by June 29, Saskatoon populations will primarily be in the third and fourth instar with first appearance of fifth instar nymphs (Fig. 4) whereas near Winnipeg development is predicted to be faster, with populations being mostly in the fourth and fifth instars (Fig. 5). Producers are advised to monitor roadsides and field margins to assess the development and densities of local grasshopper populations.
Grasshopper Scouting Steps: ● Measure off a distance of 50 m on the level road surface and mark both starting and finishing points using markers or specific posts on the field margin. ● Start at one end in either the field or the roadside and walk toward the other end of the 50 m, making some disturbance with your feet to encourage any grasshoppers to jump. ● Grasshoppers that jump/fly through the field of view within a one-meter width in front of the observer are counted. ● A meter stick can be carried as a visual tool to give perspective for a one-meter width. However, after a few stops, one can often visualize the necessary width and a meter stick may not be required. Also, a hand-held counter can be useful in counting while the observer counts off the required distance. ● At the endpoint, the total number of grasshoppers is divided by 50 to give an average per meter. For 100 m, repeat this procedure. ● Compare counts to the following damage levels associated with pest species of grasshoppers: 0-2 per m² – None to very light damage 2-4 per m² – Very light damage 4-8 per m² – Light damage 8-12 per m² – Action threshold in cereals and canola 12-24 per m² – Severe damage 24 per m² – Very severe damage For lentils at flowering and pod stages, >2 per m² will cause yield loss. For flax at boll stages, >2 per m² will cause yield loss.
Model simulations to June 13, 2021, indicate that bertha armyworm (BAW) (Mamestra configurata) pupal development is greater than 75% (Fig. 1). Populations are predominantly in the pupal stage (Fig. 2).
Model simulations indicate that BAW adult emergence has begun across southern areas of Manitoba and Saskatchewan (Fig. 3). Based on pupal development, adult emergence should occur across most of the prairies over the next few days.
Model projections to June 30 predict that development near Winnipeg is more advanced than at Lacombe (Figs. 4 and 5). The model predicts that oviposition has begun near Winnipeg and that egg hatch will begin next week in fields.
The cereal leaf beetle (CLB) (Oulema melanopus) model predicts that larval development varies across the prairies. The graph predicts development at Lethbridge (Fig. 1). The simulation indicates that populations in southern Alberta should be in the second and third instar. The appearance of pupae is expected to occur by the end of the month across southern Alberta.
Cereal leaf beetle scouting
Give priority to the following factors when selecting monitoring sites: □ Choose fields and sections of the fields with past or present damage symptoms. □ Choose fields that are well irrigated (leaves are dark green in color), including young, lush crops. Areas of a field that are under stress and not as lush (yellow) are less likely to support CLB. □ Monitor fields located along riparian corridors, roads and railroads. □ Survey field areas that are close to brush cover or weeds, easy to access, or are nearby sheltered areas such as hedge rows, forest edges, fence lines, etc.
Focus site selection on the following host plant priorities: □ First – winter wheat. If no winter wheat is present then; □ Second – other cereal crops (barley, wheat, oats, and rye). If no cereal crops are present then; □ Third – hay crops. If no hay crops or cereal crops are present then; □ Fourth – ditches and water corridors
Sweep-net Sampling for Adults and Larvae: ● A sweep is defined as a one pass (from left to right, executing a full 180 degrees) through the upper foliage of the crop using a 37.5 cm diameter sweep-net. ● A sample is defined as 100 sweeps taken at a moderate walking pace collected 4-5 meters inside the border of a field. ● At each site, four samples should be collected, totaling 400 sweeps per site. The contents of each sample should be visually inspected for life stages of CLB and all suspect specimens should be retained for identification. ● Because the CLB larvae are covered in a sticky secretion, they are often covered in debris and are very difficult to see within a sweep-net sample. ● To help determine the presence of CLB, place the contents of the sweep net into a large plastic bag for observation.
Visual Inspection: Both the adults and larvae severely damage plants by chewing out long strips of tissue between the veins of leaves (Fig. 1), leaving only a thin membrane. When damage is extensive, leaves turn whitish.
Lifecycle and Damage:
Larva: The larvae hatch in about 5 days and feed for about 3 weeks, passing through 4 growth stages (instars). The head and legs are brownish-black; the body is yellowish. Larvae are usually covered with a secretion of mucus and fecal material, giving them a shiny black, wet appearance (Fig. 2). When the larva completes its growth, it drops to the ground and pupates in the soil.
Pupa: Pupal colour varies from a bright yellow when it is first formed, to the colour of the adult just before emergence. The pupal stage lasts 2 – 3 weeks. Adult beetles emerge and feed for a couple of weeks before seeking overwintering sites. There is one generation per year.
Adult: Adult cereal leaf beetles (CLB) have shiny bluish-black wing-covers (Fig. 3). The thorax and legs are light orange-brown. Females (4.9 to 5.5 mm) are slightly larger than males (4.4 to 5 mm). They emerge in the spring once temperatures reach 10-15 ºC and the adults are active for about 6 weeks. They usually begin feeding on grasses, then move into winter cereals and later into spring cereals. Adult beetles overwinter in and along the margins of grain fields in protected places such as in straw stubble, under crop and leaf litter, and in the crevices of tree bark. They favour sites adjacent to shelter belts, deciduous and conifer forests.
Model simulations for alfalfa weevil (AAW) (Hypera postica) predict, as of June 13, that alfalfa weevil populations should be in the third larval instar (Fig. 1). Fourth instar larvae are predicted to occur across southeastern Saskatchewan and southern Manitoba.
The following graphs indicate that development is more advanced near Brandon (Fig. 2) than Swift Current (Fig. 3). Simulation runs indicate that by June 29, southern Manitoba populations will be in pupal stage whereas Swift Current populations are predicted to be in the fourth instar and pupal stages.
The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer” (Fig. 4). The green larva features a dorsal white line down the length of its body, has a dark brown head capsule, and will grow to 9 mm long.
Alfalfa growers are encouraged to check the Alfalfa Weevil Fact Sheet prepared by Dr. Julie Soroka (AAFC-Saskatoon). Additional information can be accessed by reviewing the Alfalfa Weevil Page extracted from the “Field crop and forage pests and their natural enemies in western Canada – Identification and management field guide” (2018; accessible in either English-enhanced or French-enhanced versions).
Wheat midge (Sitodiplosis mosellana) overwinter as larval cocoons in the soil. Soil moisture conditions in May and June can have significant impacts on wheat midge emergence. Adequate rainfall promotes termination of diapause and movement of larvae to the soil surface where pupation occurs. Insufficient rainfall in May and June can result in delayed movement of larvae to the soil surface. Elliott et al. (2009) reported that wheat midge emergence was delayed or erratic if rainfall did not exceed 20-30 mm during May. Olfert et al. (2016) ran model simulations to demonstrate how rainfall impacts wheat midge population density. The Olfert et al. (2020) model indicated that dry conditions may result in: a. Delayed adult emergence and oviposition b. Reduced numbers of adults and eggs
Based on averages across the three provinces, 56% of the wheat midge population is predicted to be in the larval cocoon stage (in the soil) and 44% of the larvae have moved to the soil surface. As a result of suitable temperature and rainfall, wheat midge model simulations indicate that more than 70% of the larval population has moved to the soil surface in central Alberta and northwestern and southeastern Saskatchewan (Fig. 1). Dryer conditions in Manitoba and the Peace River region continue to delay the movement of larvae to the soil surface.
More information about wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”. View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.
Aphids can cause significant damage to fields and increase crop losses but low densities in a grain field sometimes have little economic impact on production. This is especially true if the aphid’s natural enemies (beneficial insects) are present in the field because they can keep the aphids under control.
The Cereal Aphid Manager is an easy-to-use mobile app that helps farmers and crop advisors control aphid populations in wheat, barley, oat or rye. It is based on Dr. Tyler Wist’s (AAFC-Saskatoon) Dynamic Action Threshold model. The model treats the grain field as an ecosystem and takes into account many complex biological interactions including:
the number of aphids observed and how quickly they reproduce
the number of different natural enemies of aphids in the field and how many aphids they eat or parasitize per day
the lifecycles of aphids and their enemies taking into account developmental stages, egg laying behaviour, population growth rate, lifespan, etc.
Frequent in-field scouting, supported by the app’s dynamic threshold, allows growers to weigh the above factors and the app predicts what the aphid population will be in seven days and the best time to apply insecticide based on economic thresholds.
The European corn borer (ECB; Ostrinia nubilalis), has been an important pest of corn and other crops in eastern Canada for nearly a century now but is also known to be a sporadic pest in western Canada. Despite its name, ECB is actually a generalist feeder, having a wide range of hosts. With so many new emerging crops being grown in Canada that are also hosts for ECB (eg. hemp, cannabis, quinoa, hops, millet and others), there is no better time to look at this pest across the Canadian agricultural landscape.
To monitor for ECB nationwide, the Surveillance Working Group of the Canadian Plant Health Council has developed a harmonized monitoring protocol for European corn borer in both English and French. The project aims to generate real-time reporting and annual maps – access a full description of the project and list of key contact persons. The protocol can be used to report ECB eggs, larvae or damage in any host crop across Canada. This harmonized protocol has been designed to complement protocols already in use to make management decisions in order to generate data to compare ECB presence across all of Canada and across host crops.
When scouting corn, quinoa, hemp, millet, potatoes, apples, or other crops susceptible to ECB, the Surveillance Working Group of the Canadian Plant Health Council encourages the use of the harmonized monitoring protocol and reporting of the data from fields or research plots using the free Survey123 app (available for both desktop and mobile devices): • Early to Mid-Season ECB Survey (Before July) – https://arcg.is/0qCCHH (applicable for use in eastern Canada). • Later Season ECB Survey (July to Pre-Harvest) – https://arcg.is/fSODf (applicable for use in both eastern AND western Canada).
Track the migration of the Monarch butterflies as they move north by checking the 2021 Monarch Migration Map! A screenshot of the map has been placed below as an example (retrieved 17Jun2021) but follow the hyperlink to check the interactive map. They’ve reached Saskatchewan and southern Alberta!
Provincial entomologists provide insect pest updates throughout the growing season so link to their information:
MANITOBA’SCrop Pest Updates for 2021 are now available – access the June 16, 2021 report here. Be sure to bookmark their Crop Pest Update Index to readily access these reports! Also, bookmark their insect pest homepage to access fact sheets and more! • Bertha armyworm pheromone trap monitoring update for MB – Cumulative counts arising from weekly data will soon be available. • Diamondback moth pheromone trap monitoring update for MB – Refer to the summary updated twice a week. So far, only 59 traps have intercepted moths and the highest cumulative count is 135 moths near The Pas. Access the summary (as of June 8, 2021).
ALBERTA’SInsect Pest Monitoring Network webpage links to insect survey maps, live feed maps, and 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 or Twitter users can connect to #ABBugChat Wednesdays at 10:00 am. • Bertha armyworm pheromone trap monitoring update for AB – Cumulative counts arising from weekly data are starting to roll in so refer to the Live Map as data becomes available. • Diamondback moth pheromone trap monitoring update for AB – Refer to the Live Map which still reports extremely low numbers of moths intercepted so far (<45 province-wide as of 17Jun2021). • Cutworm reporting tool – Refer to the Live Map which still reports only four sites with cutworms (as of 17Jun2021).
This week’s Insect of the Week is the wheat midge. Found around the globe where wheat is grown, these small insects can pose a big problem for producers. Sizeable crop damage has been attributed to wheat midge populations across the Prairies, where it feeds on spring, winter and durum wheat, as well as triticale and spring rye.
Crop damage occurs when the wheat midge is in its larval stage. Once hatched, the wheat midge larvae eat developing wheat kernels, causing shrivelled, misshapen, cracked or scared kernels. This damage isn’t apparent at a glance and developing seeds must be inspected within the glume. Losing wheat kernels will lower crop yield, while damaged kernels will impact the grade given to the harvested wheat. The Canadian Grain Commission allows midge damage between two and five percent prior to impacting the assigned grade.
Adult wheat midges are delicate orange flies that grow to 2–3 mm long, with large black eyes and long legs and antennae in relation to their otherwise small size. Mature larvae grow to 2–3 mm long. Young larvae begin as translucent white maggots and turn bright orange during the maturation process.