Monday, July 31, 2017

UPDATE: NW MN Soybean Aphid Scouting Summary for July 21 to 28, 2017

Soybean aphid populations continue to increase in NW Minnesota. Populations are increasing in the west central and central areas, too. More fields are being treated, HOWEVER, not every field is at threshold. 

Reports for southern MN can be found at Southwest Minnesota IPM Stuff Newsletter

Comments from his July 31 report:
"Treatment of economic threshold populations are now being made in more southerly areas and the general trend is trend is economic threshold populations developing from north to south.

"Parts of Central Minnesota are receiving insecticide applications and sentinel plots at Morris had a fairly uniform 40 aphids/plant early last week. Some fields in parts of the Minnesota River Valley are at economic threshold now.

"As of last week, there were many areas of MN, including most of the SWROC, that still had low aphid populations. Winged aphids can change that quickly.

"The next two weeks will be the critical scouting window for most areas. Remember that most aphids will often be found lower in the canopy now.

"This year, much of SW Minnesota appears to have been colonized by non-local aphids."
Bruce Potter 
UMN Extension IPM Specialist


Be sure to scout a field and determine if threshold populations are present and require treatment. Issues related to pyrethroid-resistance emphasize the need to treat only when infestations are justified to prevent yield loss. Avoid unnecessary treatments to reduce the chance of finding surviving, resistant aphids and help preserve our insecticide tools for the future. 

Before making any treatment decisions, be sure to read:


We remind everyone to base treatment decisions on the threshold of 250 aphids per plant, 80% incidence and increasing populations. 

We are observing parasitic aphid activity, fungal infections of aphid colonies, and increasing numbers of predators in surveyed fields. These are all good developments that can help slow aphid population growth. In addition, the northern fields are beginning to produce winged aphids. this can produce some out-migration that can be good for infested fields but contribute to new infestations elsewhere.

The MN survey map illustrates where aphid numbers were assessed last week. Each pie chart represents a production field that was scouted. Fields are selected randomly. Scouts estimate populations on each plant sampled, placing a tally mark in the estimated # of aphid / plant range.The pie chart indicates the % plants observed within a range. Any pie charts that begin to show orange and red indicate those fields had plants with aphids into the 100's. The more red, the greater the percent plants with large infestations of aphids.This map was updated Friday (7/28/17) and reflects fields scouted Monday through Friday of last week.