Soybean aphids are infesting early planted fields

Don’t spray these soybean aphid populations yet as it could wipe out biocontrol and may flare the aphids later in July.

Soybean aphids were found last week (June 19-25) as we sampled in Saginaw, Ingham, Montcalm and Cass counties. The infested fields were planted the first or second week of May. Based on the size and number of aphids, the populations likely originated from aphids deposited in the field approximately three weeks ago. The plant infestation in fields my lab scouted ranged from 10 to 30 percent.

Do not spray these aphid populations yet. We are currently in the “battle stage.” Numerous predators and parasitoids were already recruiting to the aphid colonies, and even over a few days, the numbers of aphids per plant in some fields seem to be dropping. Also, spraying a low aphid population wipes out biocontrol and may actually flare the aphids later in July.

In addition, MSU Diagnostic Services has received several samples with spider mites in various crops. This is quite early for such calls. Spider mite is another pest flared after insecticide applications. Sit tight for now and simply check the earliest planted soybean fields that were not seed-treated.

Dr. DiFonzo’s work is funded in part by MSU’s AgBioResearch.

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