Monday, July 31, 2017

Pyrethroid resistant soybean aphids: What are your control options?

Bruce Potter (Extension IPM Specialist, U of MN), Robert Koch (Extension Entomologist, U of MN), Phil Glogoza (Extension Educator – Crops, U of MN), Ian MacRae (Extension Entomologist, U of MN), and Janet Knodel (Extension Entomologist, NDSU) 

We are receiving an increasing number of reports of pyrethroid insecticide failures for soybean aphid management from northwest and central Minnesota, and northeastern North Dakota this year. However, many areas of Minnesota and North Dakota still have low, non-yield threatening aphid numbers and scouting should continue to determine when to apply insecticides. 

In this article, we review the insecticide groups used for soybean aphid control (Table 1) and discuss the potential role of and challenges associated with insecticide mixtures. 
We are all familiar with the multistate, researched-based economic threshold of 250 aphids/plant for determining when to apply insecticides for soybean aphid. Waiting until this economic threshold to apply insecticides is KEY for ensuring continued efficacy of current insecticides for soybean aphid. Using the soybean aphid economic threshold for deciding when to apply insecticides will:

  • Prevent unnecessary selection pressure for insecticide resistance; 
  • Save time by reducing the odds of a field needing a second treatment;
  • Mitigate secondary pest problems like spider mites; and perhaps most importantly
  • Reduce production expenses.

Poor insecticide resistance management of a mobile insect like soybean aphid affects not just your farm, but other farmers as well. 

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