Manitoba Insect Update

August 3, 2009                   

Compiled by: John Gavloski, Entomologist, Manitoba Agriculture, Food and Rural Initiatives, Crops Knowledge Centre,
Phone: 204-745-5668; Fax: 204-745-5690

To report observations of insect activity or control that may be of interest or importance to others in Manitoba, please send messages to the above contact addresses.

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Summary

Aphid levels are high in some cereal fields in Eastern and Central Manitoba. Lygus bugs are numerous in some sunflower fields.

Recent Insect Concerns and Observations

Aphids in cereals: High population of aphids continue to be noticed on cereal crops in the eastern and central regions of Manitoba. The economic threshold for aphids in cereal crops is 12-15 per stem prior to the soft dough stage. Once cereal crops reach the soft dough stage aphid control is no longer likely to be economical.

Root Maggots in Canola: Although populations of many potential pests of canola have been low this summer, there are some areas where root maggots, and evidence of their feeding, are quite common. In the area around Carman it is quite easy to find root maggots or there feeding damage. In many of these fields, however, it is not obvious that the feeding has occurred unless plants are pulled to look at the roots, because otherwise the plants are still growing well. Moderate to high levels of root maggot feeding have also been reported from fields near Snowflake and Foxwarren.

Update on insects in sunflowers: As sunflowers get into the late bud stage and start to flower, it is important to scout for insects that potentially feed on the seeds. This is particularly important in confection sunflowers. So far we have not seen or heard of any high populations of seed weevils in Manitoba. Banded sunflower moth adults are showing up in pheromone-baited traps, but economical populations are not being reported. Populations of plant bugs, including lygus bugs are high in some fields. Aside from lygus bugs, there is a black species of plant bug that is more numerous than lygus bugs in many fields. We are not quite sure what this plant bug species is yet, but are working on having it identified. Many plant bug nymphs (several per head) are being found in a lot of sunflower fields. Not all look like lygus bug nymphs, but we are currently not sure what the nymphs from the black species of plant bug look like, which complicates scouting even further. When scouting sunflowers, make sure to have a good look for plant bugs. The economic injury level for lygus bugs in confection sunflowers is about 1 lygus bug per 9 heads. Lygus bugs are not likely to be economical in oilseed sunflowers.

 

Label Extensions

Lygus bugs in sunflowers: Control of lygus bugs in sunflowers has been added to the label for Matador (PCP# - 24984). Application can be by ground or air. Matador is the first, and currently only, product to be registered in Canada for control of lygus bugs in sunflowers.

 

Surveys and Forecasts

Bertha Armyworm Forecasting: Monitoring for bertha armyworm adults is complete. Remaining traps can be removed from the field. No traps exceeded 300 moths per trap over the trapping period. So all fields rated as low risk of damage from larvae. Highest cumulative counts were from the South Parkland region; Hamiota (292), Russell (274), Elkhorn (262), Miniota (250), and Shoal Lake (246). Based on this, we are not expecting it to be a bad year for bertha armyworm. Data can be viewed at:
http://www.gov.mb.ca/agriculture/crops/insects/bertha/index.html
 

Grasshopper Survey: A reminder for farm production advisors and those wanting to participate in the annual grasshopper survey that counts are done during August, when the majority of grasshoppers are in the adult stage. This year grasshopper development is later than normal, so in some areas counts may have to be delayed until adult grasshoppers are prevalent. The grasshopper survey protocol is located at: http://www.gov.mb.ca/agriculture/crops/insects/fad95s00.html