Welcome to Week 2 for the 2024 growing season! Some welcome rain for parts of the Canadian prairies and especially for some areas already coping with wildfires! This week includes: • Weather synopsis (abridged) • Flea beetles • Cutworms • Alfalfa weevil • Grasshoppers • Pea leaf weevil • Diamondback moth • Crop production guide links • Provincial insect pest report links • Crop report links
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.
Two species, Phyllotreta striolata and P. cruciferae, are the most chronic and economically important insect pests of cruciferous field crops grown across western Canada. Both species are already active so prioritize field scouting in fields of emerging and seedling canola and mustard. All cruciferous crops and plants of any Brassicaceae are similarly attractive and can suffer damage from crucifer and striped flea beetles.
If flea beetle densities are high, seedling damage levels can advance quickly – even within the same day! The cotyledon stage of canola is vulnerable to flea beetle feeding. To learn more about flea beetle damage in canola, review the current Insect of the Week (Wk 2 released May 13, 2024). Review photos of flea beetle feeding damage posted in the Weekly Update (Wk 02 – May 14, 2021) to help assess percent defoliated and to apply the action threshold of 25 % leaf area of cotyledons. The Canola Council of Canada’sCanola Encyclopedia also features flea beetles along with an excellent visual guide to help estimate feeding damage.
Jennifer Otani, John Gavloski, Kevin Floate and Meghan Vankosky
Categories
Week 2
Cutworm scouting spans April to late June across the Canadian prairies!
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 either very early or late in the day when some cutworm species (or climbing cutworms) move above-ground to feed. Start to dig below the soil surface (1-5 cm deep) near the base of symptomatic plants and also any healthy plants immediately adjacent to missing rows or wilting or clipped plants. Some cutworms feed by remaining just below the soil surface, clipping then pulling the plant below as they munch away! If the plant is well-established (e.g., perennial grass or legume), check within the crown plus in the adjacent soil. The culprits could be cutworms, wireworms, 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 to access helpful diagnostic 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: ● For anyone on the Canadian prairies, Manitoba Agriculture’s Cutworms in Field Crops fact sheet includes action and economic thresholds for cutworms in several crops, important biological information, and great cutworm photos to support in-field scouting. ● For Albertans….. If you find cutworms, please consider using the Alberta Insect Pest Monitoring Network’s “2024 Cutworm Reporting Tool” then view the live 2024 cutworm map updated daily. Review the live map to see where cutworms are appearing then prioritize in-field scouting accordingly. ● Cutworms were featured as 2024’s first Insect of the Week.
The alfalfa weevil, Hypera postica, overwinters as an adult that typically flies to alfalfa fields in April and May. Adult females start to lay eggs in May. Adults consume alfalfa foliage, but typically do not cause economic levels of damage. However, larval feeding peaks in June and, if high densities are present, can cause yield losses. Thus, field scouting to assess larval stages and densities should begin in May through to June. Review the alfalfa weevil life cycle and the damage it causes.
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 as a free downloadable PDF in either English or French on our new Field Guides page.
Jennifer Otani, Meghan Vankosky, James Tansey and Shelley Barkley
Categories
Week 2
Compared to 2023, this spring’s current weather is cooler and wetter across parts of the prairie region and those two conditions typically slow grasshopper egg development. However, grasshopper risk for the growing season remains quite high. Remember – across the majority of the Canadian prairies, 2023’s adult grasshopper densities were extremely high PLUS adults matured earlier in the season so they experienced a protracted period of egg laying (i.e., mid-June to hard frost). Already this spring, field scouts have reported finding overwintered egg pods (when normally they are difficult to locate).
As of this week, overwintered grasshopper embryos within egg pods are developing as soil temperatures warm. When 30-year normal prairie weather conditions were utilized in models, grasshopper embryos were predicted to be 50-70% developed by May 15 (Fig. 1).
Figure 1. Long-term average predicted grasshopper (Melanoplus sanguinipes) embryological development across the Canadian prairies as of May 22 based on climate normals data. Model runs were completed and mapped by R. Weiss (AAFC-Sask) as of May 22, 2022.
For the week of May 6, 2024, grasshopper nymphs were not observed in field collections at sentinel sites between Saskatoon and Kindersley, SK. For the week of May 13, 2024, first instar grasshopper nymphs were noted in initial field reports from southern Alberta (near Youngstown and Foremost), and southwestern Saskatchewan (near Outlook and Kindersley).
The 2024 grasshopper risk remains high, especially across southern Alberta and southern Saskatchewan. Field scouting is a priority across southern growing regions of the Canadian prairies for the week of May 20, 2024!
Grasshopper Scouting Tips: ● Review grasshopper diversity and photos of nymphs, adults, and non-grasshopper species to aid in-field scouting from egg hatch and onwards. ● Prioritize any area where grasshopper densities were high in 2023! ● Carefully check roadside ditches and along field edges but also check the edge of the crop and in to the actual field. ● A sweep-net can ‘detect’ grasshopper nymphs, however, economic thresholds for grasshoppers are based on the number of grasshoppers per square-metre counts. ● Access the PPMN’s Grasshopper Monitoring Protocol as a guide to help implement in-field monitoring. ● Review grasshopper lifecycle, damage and scouting and economic thresholds to support sound management decisions enabling the preservation of beneficial arthropods and mitigation of economic losses.
In the spring, overwintered adults disperse to feed upon the leaf margins and growing points of legume seedlings (alfalfa, clover, dry beans, faba beans, peas). This feeding can produce a characteristic, scalloped (or notched) edge (Fig. 1). Females lay their eggs in the soil either near or on developing pea or faba bean plants from May to June.
Figure 1. 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.
The annual pea leaf weevil survey is conducted from late May to early June. Results from the 2023 annual survey are shown in Figure 2. If you are planting field peas this year, please consider volunteering your fields for this survey. The survey is conducted by counting the characteristic ‘u’ shaped feeding notches made by adult pea leaf weevil at several locations along the field edge. Dr. Meghan Vankosky (AAFC-Saskatoon) and Dr. Boyd Mori (University of Alberta) are also seeking field sites to collect adult pea leaf weevils for laboratory experiments this spring. For these experiments, faba bean or field pea fields are being sought and weevils will be either hand-collected from plants in the field or using a sweep-net in the field margins. Please contact Meghan to volunteer field sites for adult weevil collection (meghan.vankosky@agr.gc.ca).
Figure 2. Results of the 2023 annual pea leaf weevil survey conducted in the spring of 2023.
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.
Figure 1. The life stages of the diamondback moth (Plutella xylostella), which can have multiple generations per year. Photos: AAFC-Saskatoon-J. Williams.
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. Thank you to the many people who deployed and are weekly checking traps across the BC Peace, Alberta, Saskatchewan, and Manitoba! Weekly trap interceptions are observed to generate cumulative counts.
As the season progresses, cumulative count estimates arising from these pheromone traps are broadly categorized to help producers prioritize and time in-field scouting for larvae. Preliminary data from the initial weeks of monitoring includes:
Alberta – So far, cumulative trap counts ranged from 0-10 moths with the highest interception rates arising from near Barrhead and Camrose AB. Visit Alberta Agriculture and Irrigation’s ‘live’ reporting map for updates through the 2024 growing season.
Saskatchewan – Dr. James Tansey and Carter Peru (Saskatchewan Ministry of Agriculture) shared results arising the weeks of May 1 and May 8, 2024; cumulative trap catches so far ranged from 0-16 with traps near Navscoy, Lumsden, and Coteau SK reporting the most so far.
Manitoba – Dr. John Gavloski (Manitoba Agriculture) reported that cumulative diamondback moth trap catches ranged from 0-23 for the majority of traps but that two sites reported >25 total moths. One site in the Eastern region has intercepted 33 moths and one trap in the North Interlake region has intercepted 61 moths.
Biological and monitoring information for DBM (including tips for scouting and economic thresholds) is posted by Manitoba Agriculture, Saskatchewan Agriculture, and the Prairie Pest Monitoring Network. Also, refer to the diamondback moth 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.
Every year, these guides are updated with product information and so much more! Hard copies can be purchased via the above websites but also look for the download button to access FREE downloadable PDF copies!
A few other helpful tools to keep at your finger tips:
Jennifer Otani, Shelley Barkley, James Tansey, Carter Peru and John Gavloski
Categories
Week 2
Prairie-wide provincial entomologists provide insect pest updates throughout the growing season. Follow the hyperlinks to readily access their information as the growing season progresses:
MANITOBA’SCrop Pest Updates for 2024 will start soon! Bookmark the Crop Pest Update Index to prepare for the season and also bookmark the insect pest homepage to access fact sheets and more! • Diamondback moth pheromone trap monitoring for MB – Dr. John Gavloski (Manitoba Agriculture) reported that cumulative diamondback moth trap catches ranged from 0-23 for the majority of traps but that two sites reported >25 total moths. One site in the Eastern region has intercepted 33 moths and one trap in the North Interlake region has intercepted 61 moths.
SASKATCHEWAN’SCrop Production News is coming soon. Bookmark their insect pest homepage to access important information! Access and review the Crops Blog Posts with help for scouting fields for wireworms (May 2024), grasshopper identification: pest or not (Apr 2024), a summary of wheat midge populations and management (Mar 2024), and a description of pea leaf weevil populations (Feb 2024). • Diamondback moth pheromone trap monitoring for SK – Dr. James Tansey and Carter Peru (Saskatchewan Ministry of Agriculture) shared results arising the weeks of May 1 and May 8, 2024; cumulative trap catches so far ranged from 0-16 with traps near Navscoy, Lumsden, and Coteau SK reporting the most so far. • Grasshopper hatch for SK – Week of May 13, 2024, first instar grasshopper nymphs were noted in initial field reports from southwestern Saskatchewan (near Outlook and Kindersley) and near Regina.
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. Remember, AAF’s Agri-News occasionally includes insect-related information, e.g., flea beetle control (May 6, 2024); cereal insect pests, latest on insects in canola, and post-emergence wireworm scouting (May 13, 2024). • Diamondback moth pheromone trap monitoring update for AB – Cumulative counts arising from weekly data are available so refer to the Live Map. So far, cumulative trap counts ranged from 0-10 moths with the highest interception rates arising from near Barrhead and Camrose AB. • Cutworm live monitoring map for AB – Cumulative counts arising from weekly data are available so refer to the Live Map. • Grasshopper hatch for AB – Week of May 13, 2024, first instar grasshopper nymphs were noted in initial field reports from southern Alberta (near Youngstown and Foremost).
