Check corn fields for western bean cutworm in early September

Walking into fields to scout for western bean cutworms will help you identify damaged grain that should be stored separate from the good.

I’m urging growers to check corn fields in the next few weeks to detect nasty cutworm “surprises.” I have been to a few fields north of Lansing that are heavily infested with western bean cutworms, and it’s something you can’t detect unless you walk into the field. Western bean cutworms will be in the ear tip, although some are getting big enough to drop to the ground to overwinter. To help identify infested ears, look for a missing silk mass, husks slightly open at the top, or a moist, “pooey” mass in the tip.

Grain from heavily infested fields is often in poor condition (damaged kernels) and of poor quality (fungal infestation), and thus should be stored separate from good grain. Grain in poor condition is also a primary candidate for grain beetle infestation, so storing it for a long period on-farm isn’t wise.

Priority fields for scouting are

  • Non-Bt fields and refuge areas.
  • Bt corn that doesn’t control western bean cutworms (Yieldgard, VT double/ triple pro, original Agrisure hybrids).

Bt corn with Cry1F has a less chance of infestation (Herculex, OAM1, Smartstax) and Agrisure VIP corn has an even less chance, but if you find local heavy infestations in non-Bt corn, you may check these fields to see a comparison of control.

The priority location for scouting is the western half of Michigan, especially:

  • Counties on the border with Indiana (high trap catch)
  • Central Michigan western bean cutworm “black hole area” (Montcalm, Gratiot, Mecosta, Isabella, Ionia, Clinton counties)
  • Northwest counties around Traverse City, Mich. (historic high infestations)

The Thumb region is a lower priority, as it has had low flights and few reports of infestations in the past. However, there was one report of western bean cutworms in sweet corn in Sanilac County this year.

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

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