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Aphid populations can quickly increase at this point in the season and particularly when growing conditions are warm and dry. Access the Provincial Insect Pest Report for Wk15 to remain alert to areas and crops suffering from aphid pest pressure.
Figure 1. Pea aphid adults (each 3-4 mm long) and nymph. Photo: M. Dolinski.
Alternatively, several aphid pest species are described in the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) and is accessible as a free downloadable PDF in either English or French on our Field Guides page. PDF copies of the individual pages have been linked below to access quickly: • Corn leaf aphid or Rhopalosiphum maidis (Fitch) • English grain aphid or Sitobion (Macrosiphum) avenae (Fabricius) • Oat-birdcherry aphid or Rhopalosiphum padi (Linnaeus) • Pea aphid or Acyrthosiphon pisum (Harris) • Potato aphid or Macrosiphum euphorbiae (Thomas) • Soybean aphid or Aphis glycines (Matsumura) • Turnip aphid or Lipaphis erysimi (Kaltenbach) • Sugar beet root aphid or Pemphigus betae Doane • Russian wheat aphid or Diuraphis noxia (Mordvilko)
Access the Provincial Insect Pest Report for Wk15 for updates for this economic insect pest.
Remember: in-field scouting is required to apply the economic threshold to manage both this pest and its natural enemies. Use the images below (Fig. 1) to help identify moths from the by-catch that will be retained in the green phermone-baited unitraps.
Figure 1. Stages of bertha armyworm from egg (A), larva (B), pupa (C), to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada).
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also, refer to the bertha armyworm 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.
Scouting and pest management for diamondback moth depends on in-field counts of larvae per metre2! This means plants need to be pulled and tapped off to assess the number of larvae! Use Figure 1 below to help identify the different stages of the diamondback moth.
Figure 1. The life stages of the diamondback moth (Plutella xylostella), which can have multiple generations per year. Photos: AAFC-Saskatoon-J. Williams.
The economic threshold for immature and flowering canola is 100-150 larvae per metre2.
Access the Provincial Insect Pest Report for Wk15 for updates for this economic insect pest.
Jennifer Otani, Hector Carcamo and Meghan Vankosky
Categories
Week 15
Access the Provincial Insect Pest Report for Wk15 for updates for this economic pest.
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.
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. ● It is best to scout on warm days when grasshopper nymphs are more active and easier to observe. ● Carefully check roadside ditches and along field edges but also check the edge of the crop and into the actual field. ● Younger or earlier instar nymphs are easier to manage – visit sites every few days to stay on top of local field conditions. ● 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.
Important – A preliminary summary of available thresholds for grasshoppers has been kindly shared by Dr. J. Tansey (Saskatchewan Agriculture) in Table 1. When scouting, compare in-field counts to the available threshold value for the appropriate host crop AND for field or ditch situations. Available thresholds (nominal and economic) help support producers while protecting beneficials (i.e., predators, parasitoids, and pathogens) that regulate natural populations of grasshoppers.
Access the Provincial Insect Pest Report for Wk15 for updates for this economic insect pest.
Two species of crickets can be found in more southern regions of the Canadian prairies. The Mormon cricket (Anabrus simplex Haldeman) is typically active as an adult from late June to mid-September. Host plants for the nymphs and adults include broad-leafed plants but they will also feed on sagebrush, grasses and small shrubs, as well as wheat, barley, alfalfa, sweet clover, some forages and garden vegetables plus other insects. Fall field crickets (Gryllus pennsylvanicus Burmeister) are normally observed from late July to the end of September. Fall field crickets (nymphs and adults) can feed and affect seed yields in forages grown for seed, cereals, and some small fruits when they occur at high densities, however, fall field cricket adults are predators of grasshopper eggs.
Biological and monitoring information for fall field cricket (Gryllus pennsylvanicus Burmeister) and Mormon cricket (Anabrus simplex Haldeman) are described in the cricket 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 Field Guides page.
While the PPMN no longer predicts the development of Culex tarsalis, the dominant vector for West Nile Virus(WNV), areas of the Canadian prairies in 2024 have received high levels of precipitation. This is noteworthy because the larvae of C. tarsalis can develop in, “agricultural tailwater, alkaline lake beds, fresh and saline wetlands, secondary treated sewage effluent and oil field run-off” (Centre for Vector Biology URL retrieved 2024Jul04).
Culex tarsalis have a base developmental threshold of 14.3 °C. Across the Canadian prairies, WNV transmission is of greatest concern as the second generation of C. tarsalis females begin to fly (by 250-300 degree days). In fact, an additional 109 degree days (using Base 14.3 °C) is required within a given mosquito population for virus development to complete to the point that transmission might occur.
Historically, by mid-July, C. tarsalis adults begin to fly in southern parts of the Canadian prairies. By August, protect yourself from mosquitoes when outdoors – this is the window when mosquitoes are most numerous plus have the greatest chance of carrying WNV. Field scouts and outdoor enthusiasts should wear DEET to protect against C. tarsalis and WNV.
For reference, the following table of data was quickly generated using AAFC Drought Watch Historical Daily Air Temperatures since April 1, 2024:
Location
Degree Days (base 14.3 °C) as of August 13, 2024
Observed date heat units >200 Degree Days
Potential date when >200 Degree Days attained
Potential date when >390 Degree Days attained
Winnipeg
330.6
July 20
—
August 28
Saskatoon
266.2
July 29
—
Unable to project
Lethbridge
294.7
July 25
—
Unable to project
Edmonton
188.6
—
August 18
Unable to project
Grande Prairie
220.9
August 11
—
Unable to project
Note: Potential dates calculated using daily mean of 18°C until August 30, 2024, then daily mean of 15°C for September 1-30, 2024.
As harvest approaches, remember to consider PHI before applying pesticides for late-season pests. The PHI refers to the minimum number of days between a pesticide application and swathing or straight combining of a crop and reflects the time required for pesticides to break down after being applied. PHI values are both crop- and pesticide-specific. Adhering to the PHI is important for a number of health-related reasons and to ensure that crops being sold for export meet pesticide residue limit requirements.
Jennifer Otani, John Gavloski, Shelley Barkley, James Tansey and Carter Peru
Categories
Week 15
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 are available. Access the August 15, 2024 report (or access the PDF copy). Bookmark the insect pest homepage to access fact sheets and more! Highlights reported by Dr. J. Gavloski include: • Bertha armyworm – “Continues to be noticed at high levels in some canola fields in the Southwest region and western part of the Central region. Access Manitoba’s fact sheet for this insect to support in-field scouting for larvae now. • Lygus bugs – “High levels were noted in some canola fields in the Northwest and Easter regions”. Review the report for scouting tips and photos of lygus bug adults and nymphs. • Aphids – “Soybean aphids have been increasing in some areas but no reports yet of economic levels or insecticide applications” being applied so far. • Green caterpillars in canola – Review the report for tips and photos to differentiate a number of species that can be present now in canola. • Grasshoppers – The annual grasshopper survey is underway now. Interested participants can find the protocol, data sheet, and steps to submit data in the newly updated protocol. • Reminder – Insects in Stored Grain – AAFC in Winnipeg is seeking producer participation for grain bin monitoring in September-October 2024. Learn more here and find out how to participate.
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, AAI’s Agri-News occasionally includes insect-related information, e.g., diamondback moth and bertha armyworm (August 6, 2024); aphids in field crops, canola flower midge scouting (July 29, 2024); assessing and a description of missing pods on canola (July 22, 2024); scout for wheat midge (July 15, 2024); the right canola crop stage to spray for lygus bugs (July 8, 2024); soil moisture, wheat midge and other insect pests (June 24, 2024); scout for grasshoppers and other insect pests (June 17, 2024); how to manage stem feeding from flea beetles, keep canola bins malathion-free, scout for grasshoppers and other pests (June 10, 2024); scout for insect pests (June 3, 2024); scout for grasshoppers (May 27, 2024); flea beetle control (May 6, 2024); cereal insect pests, latest on insects in canola, and post-emergence wireworm scouting (May 13, 2024). • Wheat midge monitoring – Cumulative counts arising from weekly data are available so refer to the Live Map (as of August 1, 2024). • Cabbage seedpod weevil monitoring – Sweep-net count data can be reported here then the data populates the Live Map (as of August 8, 2024). • Diamondback moth monitoring – Cumulative counts arising from weekly data are available so refer to the Live Map (as of July 4, 2024). Remember to scout fields for larvae. • Bertha armyworm pheromone trap monitoring – Cumulative counts arising from weekly data are available so refer to the Live Map (as of August 8, 2024). Remember to scout fields for larvae.
