Western bean cutworm special alert

Start scouting now for western bean cutworms, as flight increased over the weekend and peak is approaching this week or next.

Western bean cutworm flight increased over the weekend (July 16-17). They may be at peak this week or early next week. This is earlier than previous years. If you scout corn for western bean cutworms, start now.

Egg masses were found in some fields I walked in central Michigan on corn approaching pre-tassel stage. Some of these eggs were already hatching. With the hot weather, I estimate only four days from deposition to hatch, so it might be easy to miss egg masses altogether in a field.

In dry areas, irrigated fields may be very attractive to females. I am not so concerned about shorter corn. Desperate females may lay eggs on whorl-stage plants, but larvae can’t survive – they seem to need reproductive tissue (tassel or silk) to survive.

What about dry beans? A difficult question! We know western bean cutworm larvae feed on flowers and small pods, but the most important damage is to bigger pods. My best guess is that peak flight will be sometime during the week of July 25, with optimal spray timing just after. Don’t spray just yet, but be prepared in the next two weeks. We will continue to monitor flight and field populations, and send out a message next week to help time the dry bean applications.

Western bean cutworm egg mass
Western bean cutworm egg mass just deposited.

3 day old egg mass
Western bean cutworm mass about three days old.

Hatched egg mass
Western bean cutworm egg mass hatched.

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

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