Thursday, July 16, 2015

It's Time to Keep Track of Soybean Aphid Populations in Your Fields

Post was updated July 20, 2015

Soybean fields are being scouted in the region, with particular emphasis on soybean aphid and how populations are establishing and increasing.

Though field populations of aphids are quite variable, populations certainly are increasing as we would expect for this time of year. The majority of the fields we've scouted in the past two weeks were averaging under 20 aphids per plant HOWEVER we did have a few fields average from 50 - 60 aphids plant. In fields with these greater averages, the percent plants with aphids present were in the 90+ % range. Also within those greater number fields, we are finding randomly selected plants reaching into the 200+ aphid counts, though those plants represented only about 15% of the total plants randomly selected at individual sites.

The Downside of Insurance Insecticide Applications for Soybean Aphid

by Robert Koch (Extension Entomologist), Bruce Potter (IPM Specialist), Jeff Gunsolus (Extension Weed Scientist) 

For soybean aphid management, we encourage you to rely on scouting (actually getting into the field and looking at plants) and the validated economic threshold (average of 250 aphids per plant, aphids on more than 80% of plants, and aphid populations increasing) to determine when to apply insecticides for soybean aphid (see "Scouting for soybean aphid"). The threshold number of aphids is below the number required to cause yield loss and allows time to apply an insecticide before economic loss is incurred. However, you might be tempted to apply insecticides for soybean aphids at low population levels or without regard to the size of the aphid population in field, just in case you might have a problem. These "insurance" applications of insecticides can have negative impacts.