Dr. Eileen Cullen, University of Wisconsin Extension Entomologist
As note last week, it is time to scout for soybean aphids and be aware of current population densities in your fields to determine if they are increasing toward the economic threshold.
This week, a new video was added called “Scouting Soybean Aphids” which breifly demonstrates scouting and discusses management in Wisconsin fields.
[youtube]http://www.youtube.com/watch?v=gZTzbroDnws[/youtube]
Economic threshold is reached when a field average is 250 aphids/plant and populations are actively increasing. To calculate a field average, count the number of aphids on each of 20-30 plants/field, from a sample representative of at least 80% of the field.
Begin field scouting in late June (late vegetative to beginning bloom soybean growth stages), making one or two visits/field/week. Continue scouting until aphid populations decline, usually mid to late August.
Key publications:
Should I Spray for Soybean Aphid?
https://ipcm.webhosting.cals.wisc.edu/download/pubsPM/sba2010-web.pdf
Pest Management in Wisconsin Field Crops (A3646)
http://learningstore.uwex.edu/Assets/pdfs/A3646.pdf