You Are Here: Management Updates 2006 Archive June 1, 2006

Date: June 1, 2006
Category: Insects
Subject: Bronzed Cutworms

We just received a sample of "hale and hearty" caterpillars from a golf course just north of Sebago Lake in Maine. They turned out to be "bronzed cutworms" (Nephelodes minians). They were collected from some tall ryegrass sites and were active near the roots, not feeding on foliage like so many cutworms.

Bronzed cutworms (BZCW) have a very different life cycle than most of the caterpillars we find in New England. According to textbooks, moths are present in the fall and lay eggs in October or November. Eggs hatch into caterpillars in late winter. In fact, feeding sometimes occurs under snow cover and small larvae may destroy much of the foliage by the time the snow melts in spring. Larger
larvae then make their way deeper in the profile, often feeding deep within the crown. Larvae in New York normally complete their development between mid May and mid June, and then form pupae in the soil. Those pupae persist until fall, when the new adults emerge and repeat the process.

Small BZCW larvae often are green, while the larger stages are brown on the "top" side and lighter colored below. The caterpillars have a broad, well-defined, yellow middorsal strip, along with other lighter colored stripes along the side of the body. The really distinctive feature is a set of alternating stripes on a sclerotized dark plate just behind the head. The base color of the plate is black or very dark brown, but there are three narrow yellow stripes running parallel to the body as well.

The caterpillars that were sent to us were more than an inch long, very close to their full size. In most cases insecticide treatment probably is not warranted at this point, because the larger instars are much harder to control and they should be finished feeding within a week or two. In limited situations, an application of carbaryl might help. (Remember to check the water pH.) Pyrethroids or chlorpyrifos, ordinarily used for black cutworms, might be less appropriate in this case because BZCW caterpillars are active so much deeper in the profile so you need a more mobile product.

But for most of you, try to ride this one out - and make a note to look for caterpillar activity earlier next spring!

Submitted by: Dr. Pat Vittum

DISCLAIMER - As always, it is the responsibility of the applicator to verify the registration status of any pesticide BEFORE applying it. Different states have different regulations as well. The author and the University of Massachusetts are not liable for any consequences of any pesticide "recommendations". Mention of any trade name is not to be considered endorsement of a product.

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