Week 2 and it’s time to get busy with in-field scouting for insects – cutworms, wireworms, flea beetles, and more are all active! In addition to the Weekly Update, be sure to catch the Insect of the Week.
Now, more than ever, we wish everyone a safe and productive field season! Stay Safe!
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.
This past week (May 3-9, 2021), the average temperature across the prairies was 1.3 °C cooler than normal (Fig. 1). Similarly, the average 30-day temperature (April 10-May 9) was 1.7 °C less than climate normal values (Fig. 2). Temperatures have been warmest in southern Alberta (Table 1; Fig. 1-2).
The growing degree day map (GDD) (Base 5 ºC, April 1-May 2, 2021) is provided below (Fig. 3) while the growing degree day map (GDD) (Base 10 ºC, April 1-August 9, 2020) is shown in Figure 4.
At this early point in the growing season, cool temperatures pose the risk of frost but the differences between low and high temperatures can exert incredible stress on newly germinating plants in field crops. The lowest temperatures recorded ranged from <-59 to >-6 °C (Fig. 5) while the highest temperatures (°C) observed across the Canadian prairies the past seven days ranged from <11 to >26 °C (Fig. 6). Wow, what an amazing range – spring is tough!
Seven-day cumulative rainfall indicates that below normal rain (86% of average) was reported for the prairies (Fig. 7). Over the past seven-days rain totals across most of Alberta and the extreme southwest region of Saskatchewan was 10-20 mm. The rest of the prairies received little or no rain. Rain (30-day accumulation) amounts have been less than average for most of the prairies (81% of average). Rainfall for April 10-May 9, 2021, has been greatest for southeastern Manitoba, southwestern Saskatchewan and across most of Alberta (Table 1; Fig. 8). Average growing season (April 1 to May 9) precipitation has been well below average for most of the prairies. The two large regions (Swift Current to Prince Albert to Vegreville and the western two-thirds of Manitoba) have had less than 40 % of normal precipitation.
Agriculture and Agri-Food Canada (AAFC) and Environment and Climate Change Canada (ECCC) 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.
‘Forward trajectories’ have a similar purpose; however, the modeling process begins at sites in USA & Mexico. The model output predicts the pathway of a trajectory. Again, of interest to us are the winds that eventually end up passing over the Prairies.
1. REVERSE TRAJECTORIES (RT) Since May 1, 2021, the majority of reverse trajectories crossing the prairies originated from the Pacific Northwest (Idaho, Oregon and Washington). This week, an increasing number of reverse trajectories have been moving north from Kansas and Nebraska (Fig. 1).
a. Pacific Northwest (Idaho, Oregon, Washington) – The majority of Pacific Northwest reverse trajectories have been reported to pass over southern Alberta (Fig. 2).
b. Mexico and southwest USA (Texas, California) – Since last week there have not been any trajectories that originated in these areas that have crossed the prairies.
c. Oklahoma and Texas – Since last week there have not been any trajectories originating in Oklahoma or Texas that have crossed the prairies.
d. Kansas and Nebraska – This week reverse trajectories were reported for Alberta (Andrew, Sedgewick), Saskatchewan (Gainsborough, Grenfell, Kindersley, Regina, Yorkton) and Manitoba (Brandon) (Fig. 3).
2. FORWARD TRAJECTORIES (FT) Forward trajectories, originating from Mexico and USA have crossed a number of prairie locations since May 1, 2021. Based on average totals (averaged across a five day period), the greatest number of forward trajectories were observed to originate between May 5 and 8 (blue bars) and entered the prairies between May 6-9 (Fig. 4).
The following map presents the total number of dates (since March 24, 2021) with forward trajectories that have crossed the Canadian prairies (Fig. 5). Results indicate that the greatest number of forward trajectories entering Canada originated from the Pacific Northwest (Idaho, Oregon, Washington).
‘Tis the season…. to scout for cutworms! Scout fields that are “slow” to emerge, are missing rows, include wilting or yellowing plants, have bare patches, or appear highly attractive to birds – these are areas warranting a closer look. Plan to follow-up by walking these areas later in the day when some cutworm species move above-ground to feed. Start to dig below the soil surface (1-5 cm deep) near the base of a symptomatic plant or the adjacent healthy plant. If the plant is well-established, check within the crown in addition to the adjacent soil. The culprits could be wireworms, cutworms, or more!
Important: Several species of cutworms (Lepidoptera: Noctuidae) can be present in fields. They range in colour from shiny opaque, to tan, to brownish-red with chevron patterning. A field guide is available to help growers scout and manage the various species of cutworms that can appear in field crops grown on the Canadian prairies. Cutworm Pest of Crops is available free in either English or French! Download a searchable PDF copy that includes great photos plus a table showing which larvae are active at different points in the growing season!
Other vital resources to scout and manage cutworms include:
Newly seeded fields should be scouted throughout the germination and emergence periods for a variety of insect pests – one of the most difficult to detect can be wireworms! Wireworms are the juvenile stages of a complex comprised of several species of Elateridae, commonly referred to as ‘Click beetles’. On the Canadian prairies, wireworm collections from field crops indicate that three economically important species of wireworms or click beetles can be present; Selatosomus destructor, Limonius californicus, and Hypnoides bicolor. According to van Herk and Vernon (2014), a wide variety of Elateridae have been described from across the Canadian prairies; Alberta 144 species described in Alberta, 108 species described from Saskatchewan, and 109 species described from Manitoba.
Review these two wireworm posts to learn more and supplement in-field scouting:
The cereal leaf beetle (CLB) model output suggests that overwintered adults are active and that oviposition is underway across the prairies. The graphs provide a comparison of development for Saskatoon (Fig. 1) and Winnipeg (Fig. 2). The simulation indicates that first instar larvae may occur during the third week of May.
Lifecycle and Damage:
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). 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 shelterbelts, deciduous and conifer forests. 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.
Egg: Eggs are laid approximately 14 days following the emergence of the adults. Eggs are laid singly or in pairs along the midvein on the upper side of the leaf and are cylindrical, measuring 0.9 mm by 0.4 mm, and yellowish in colour. Eggs darken to black just before hatching.
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. 4). 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.
The grasshopper simulation model will be used to monitor grasshopper development across the prairies. Weekly temperature data collected across the prairies is incorporated into the simulation model which calculates estimates of grasshopper development stages based on biological parameters for Melanoplus sanguinipes (Migratory grasshopper).
Model simulations were used to estimate percent grasshopper embryonic (egg) development as of May 9, 2021. The simulation predicts that development has now begun across southern areas of the Peace River region. Results indicate that egg development has been greatest for Lethbridge and Regina regions. Cool conditions in Manitoba have resulted in slower development rates (Figs. 1 and 2).
Model simulations for alfalfa weevil (AAW) indicate that oviposition should be well underway across the prairies. The following graphs indicate, based on potential number of eggs, that development is more advanced near Lethbridge (Fig. 1) than Brandon (Fig. 2). The model predicts that hatch may occur during the last week of May.
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).
Diamondback moth pheromone trap monitoring update for SK – two moths were reported (2021May13 Tansey, pers. comm.); one moth near Shaunavon (RM78) and one moth near Raymore (RM 278).
• ALBERTA’SAlberta Insect Pest Monitoring Network webpage links to insect survey maps, live feed maps, and insect trap set-up videos and more. Additionally, NEW for 2021 – AAF’s Shelley Barkley has gathered and streamlined information into a Major Crops Insect webpage. The new webpage does not replace the Alberta Insect Pest Monitoring Network page. However, the new Major Crops Insect webpage serves as a table of contents, connecting users to crop insect pest information on alberta.ca. It offers links to specific insect identification, life cycle, damage, monitoring and management. Users will hopefully find pertinent insect information with fewer clicks! Remember, AAF’s Agri-News occasionally includes insect-related information or Twitter users can connect to #ABBugChat Wednesdays at 10:00 am.
Diamondback moth pheromone trap monitoring update for AB – Refer to the Live Map which reports zero moths (as of 13May2021).
Cutworm reporting tool for AB – Refer to the Live Map which reports two sites with cutworms (as of 13May2021).
In canola, the most common flea beetles are either bluish black (crucifer flea beetle or Phyllotreta cruciferae) or black with two wavy yellow lines running down the length of its back (striped flea beetle or P. striolata). They overwinter as adults under plant material along field margins and females lay eggs in the soil near host plants.
Striped and crucifer flea beetles feed on canola, mustard and related cruciferous plants and weeds. Canola is highly susceptible to feeding damage at the cotyledon stage – damage appears as ‘shot-holes’ in cotyledon leaves. Flea beetles also feed on stems and very young seedlings may wilt or break off under windy or damp conditions. New generation adults feed on maturing pods late in the summer. Remember, the Action Threshold for flea beetles on canola is when 25% of cotyledon leaf area is consumed (see post from 2019 on estimating flea beetle damage and action threshold and the Flea Beetle Monitoring Protocol).
According Dr. Tyler Wist (@TylerWist1), who makes it his business to know, striped flea beetles are already active.
ECCC trajectory models indicate that air trajectories, originating over the Pacific Northwest (Idaho, Oregon, Washington), have crossed one Saskatchewan location (Unity) and a number of Alberta locations including Lethbridge, Beiseker, Olds, Provost, Vegreville, Andrew, Grande Prairie, Rycroft and Fort Vermillion.
Access this DAILY one-page report to learn more. Albertans and Saskatchewanians please take note!
Areas highlighted green in this alert may receive incoming winds from the Pacific Northwest of the USA very shortly! Remember, host plants of diamondback moth include all plants in the Brassicacea family, including cruciferous weeds and volunteer canola. These plants are suitable hosts until canola emerges.