Good News! Infestations in NW Minnesota and eastern North Dakota are generally low. Populations in SW MN are increasing according to Bruce Potter, IPM Specialist in Lamberton. He is anticipating populations reaching treatable levels across that area next week.

Increases to the south typically signal the start of migration events that result in winged soybean aphid moving into this region. It is now time to keep notice of how aphid populations are developing in area fields and respond accordingly.

Remember, our treatment threshold is 250 aphids/plant, when 80% of plants have aphids and populations are growing. Last week’s newsletter provided the overview of speed scouting as a quick method for sampling and deciding whether fields require treatment. Still a little confused about Speed Scouting? Iowa State University has just posted a web based exercise that runs you through the speed scouting method, allows you to fill in the worksheet, and show you the decision process. Check it out at:

http://www.ent.iastate.edu/soybeanaphid/speedscouting/

Do higher temperatures mean insect activity is hot, hot, hot? 
Not necessarily....

Soybean Aphid - The high temperatures will probably slow soybean aphid population growth in many areas.  This may delay the development of treatable aphid populations and allow natural enemies (relatively numerous this year) to better control aphid numbers. Although there is conflicting literature, in generalities, the efficacy of most Synthetic Pyrethroids suffers when temperatures are much above 90F. Lorsban or one of the other Organophosphates may be a better choice for soybean aphid control during periods of high heat (>90F). There have been reports of this phenomenon in the past several years when treating aphids during really hot spells.

Two-Spotted Spider Mites - These may be another looming problem in some locations.  West Central and SW MN have been increasingly dry this season, though not widespread in NW.  Combined with high temperature, these are ideal conditions for two-spotted spider mites. For more info on spider mites, including scouting protocols and thresholds, and pictures, go to:

http://www.soybeans.umn.edu/crop/insects/spider_mites.htm