Skip to main content

Regional Soybean Aphid Update: August 3, 2018

The joint MN-ND soybean survey map provides a regional perspective on where aphid activity is most significant. Scouting is important before making any treatment decisions. 

Here are the summary of observations for Aphids/plant estimated for scouted fields over the past two weeks. Fields in the central area are reaching threshold and are justifiably being treated. Some of those treated fields have been in our survey fields.

The next two MN survey maps illustrates aphid numbers for each production field scouted as a pie chart. 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 showing orange and red indicate those fields had plants with aphids into the 100's. The more orange to red, the greater the percent plants with larger numbers of aphids.These maps were created Friday, July 27 and August 3, respectively. Note that the symbols overlap each other. The symbol for the more heavily infested fields will always be layered on top in the graphic and not hidden.

Aphid updates and other important crop updates can also be found at Southwest Minnesota IPM Stuff Newsletter prepared by Bruce Potter, UMN Extension IPM Specialist. Subscribe or follow the link to read his updates. 

Treatment Decisions:  Pyrethroid Resistance Complicates Decisions 

Be sure to scout fields BEFORE making a treatment decision. Avoid the temptation to treat below threshold numbers because it is "cheap", or for convenience or ‘insurance’; this is bad management. Insecticide resistance means management will no longer be easy or cheap. 

These non-threshold-based approaches have put us in a difficult position. You should have heard or read plenty of information this winter about Pyrethroid Resistance in soybean aphid. Insecticide treatments place selection pressure on the population to find survivors. Treating frequently increases the likelihood that you find those survivors sooner. 

Control problems with Pyrethroids are being reported in areas where applications are being made. Please review your aphid management options. 

Aphid insecticide resistance summary: 

Populations of soybean aphid resistant to pyrethroid insecticides, such as bifenthrin and lambda-cyhalothrin (Group 3 insecticides), have been detected in Minnesota over the last three years. This year, preliminary results from laboratory bioassays with soybean aphids collected earlier this week from a field near Willmar once again suggest some level of soybean aphid resistance to pyrethroids. Because of this recent history of issues with pyrethroids for management of soybean aphid, we currently discourage the use of products containing only a pyrethroid insecticide. Generally speaking, products containing a single active ingredient from a labeled insecticide group other than Group 3 are preferred over mixtures when resistance management is a goal. However, with the limited number of insecticide groups available for soybean aphid, mixtures of insecticides will likely play a role in alternations. After treating a field, be sure to scout the field after 3-5 days to ensure efficacy of the treatment. If a field needs to be retreated, alternate to a product containing a different insecticide group for the follow-up treatment. Check product labels for insecticide group numbers. For further information, see our recent publication on managing insecticide resistant soybean aphids

If a treatment decision is made, consider efforts to protect pollinators that will be active in fields at this time of year. More details are summarized at:

Print Friendly and PDF