by Robert Koch (Extension Entomologist), Bruce Potter (IPM Specialist), Ian MacRae (Extension Entomologist), and Ken Ostlie (Extension Entomologist)
Soybean aphid populations in many areas of Minnesota are increasing. This year, there are a number of factors making population development and management less predictable than in the previous couple of years:
- Late summer dispersal of soybean aphids is currently occurring, bringing high numbers of winged aphids to colonize fields; sometimes those that were previously treated.
- Forecasted weather conditions for the upcoming week look favorable for aphid population growth.
- A number of fields in southwestern Minnesota have reported unexplained failure (poor performance) of recent insecticide treatments and will require additional applications to control existing populations.
If a field needs to be treated more than once in the same year, remember the potential for development of insecticide resistance (U of MN fact sheet on insecticide resistance). Do not reapply the same insecticide mode of action (insecticide group). For example, if a field was treated with an organophosphate insecticide and needs to be treated again for aphids or some other pest, such as spider mites, avoid using organophosphates for the second application. Instead, use a different insecticide group, such as a pyrethroid. The mode of action (or group) is on most insecticide labels.