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Soybean Aphid Update (07/20/17)

Continue scouting for soybean aphids. Soybean aphid is slowly increasing and still below economic threshold in most fields.

Soybean Aphid Update

                Continue scouting for soybean aphids. Soybean aphid is slowly increasing and still below economic threshold in most fields. The area with highest populations, above the economic threshold (250 aphids per plant and 80% incidence and an increasing populations) is in Grand Forks and Walsh counties, based on conversations with crop consultants in that area. Avoid the temptation to make early ‘insurance’ insecticide applications below the economic threshold. We often hear the excuse that insecticides are cheap or the second application is ‘free’ from the chemical company. However, profit margins are tight this year and if you do not have an economic population of soybean aphids, you do not have a population of aphids that would cause yield loss and this unnecessary spraying will increase the cost of production. Spraying when economic populations of soybean aphids are not present also will lead to killing off the natural enemies and a resurgence of soybean aphids later in season, or aggravating secondary insect pests like spider mites. Spraying twice with the same product will lead to increased risk of insecticide resistance in soybean aphids. Minnesota has documented a resistance in soybean aphids to pyrethroid insecticides: 4x to bifenthrin and 10-20x to lambda-cyhalothrin. We definitely want to prevent any insecticide resistance. Finally, if you apply the insecticide by ground, you are driving over the soybeans, reducing yield from wheel traffic, and taking more money out of your profits.

 

Patrick Beauzay                                                                                                              

Research Specialist, Extension Entomology      

                                                   

Janet J. Knodel

  Extension Entomologist

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