August 24, 2007

We have received several reports of green cloverworms in soybeans in south central and central Nebraska recently. Some fields have been treated in the last week. These caterpillars are periodic pests of soybeans in the Midwest. Green cloverworm larvae are pale green with two white stripes running down the length of each side. Another distinguising characteristic is the presence of three pairs of abdominal prolegs, and one anal proleg, in addition to the three pair of legs on the thorax. They reach about one inch in length at maturity.

In some locations fungal pathogens have been observed killing the caterpillars. The warm wet weather we have been having in many areas increases the possibility of insect pathogenic fungi attacking insects.

Check your soybeans for the presence of green cloverworms or other defoliating insects. If defoliation levels exceed 20% and caterpillars are present, an insecticide application may be warranted. See the UNL Department of Entomology Web site for pest management at http://entomology.unl.edu/instabls/soydefol.htm for information on insecticides labelled for use in soybeans, their rates, and preharvest intervals.

Bob Wright
Extension Entomologist, Lincoln