SW MN IPM Stuff 2019 IPM Note

10/7/19

Greetings:

I spent a couple hours at Farmfest 2019 this morning and had a chance to visit with some friends. Many of the comments revolved around the lack of soybean aphids this year. While this may be true in most cases, there are starting to be more and more exceptions.

Over the past week, aphid populations have dramatically increased in some areas. This afternoon, Curt Burns and Regan Olson called to report populations nearing threshold. Andy Nesseth reinforced those observations. All of them commented that fields near bodies of water seemed to be more heavily infested. (There are several possible reasons why that may be the case...ideas?)

Observations from fields I have personally visited or received reliable reports seem to indicate that populations tend to be higher in a north-south line roughly through portions of Kandiyohi, Renville, Brown, Watonwan, Martin, and Jackson Counties. It is highly probably that some of the fields in other areas may reach threshold levels (80% or more of the plants with aphids, 250 aphids/plant average, aphids increasing).

Obviously, aphid populations vary by geographic area and from field to field. Some things to key in on scouting are: geographic areas where some soybeans were planted early, geographic areas where rainfall has been low the past couple weeks and fields that are smaller and in sheltered areas. As the season progresses later planted soybeans will be more attractive and it appears that this shift is starting now.

  • This is intended as a reminder to not give up on aphids to early.
  • This is not intended as advice to spray. 
  • Reports of aphid populations from other areas and other fields are likely to be worthless for your own! There are too many variables. Scouting pays. 
  • Remember, soybean aphid populations are likely to be, at least in part, resistant to pyrethroid insecticides.
  • If you applied an insurance insecticide a week or more ago, you may be practiced up to spray again for real.
  • The next 1-2 weeks are going to tell the tale.

Happy trails,
Bruce