June 18, 2010

We have received several reports of caterpillars damaging seedling soybeans in southeastern Nebraska. In cases where we have received samples, the caterpillars have included yellow-striped armyworms and green cloverworms. In some cases, the caterpillars may have begun feeding on winter annual weeds in or near the field before planting and now that soybeans have emerged and the weeds have been removed, the caterpillars have moved over to soybeans.

Soybeans can withstand considerable defoliation in the seedling stage. Once past seedling stages, consider treatment for vegetative soybeans if the insects are present and defoliation will reach 40%. Assess the distribution of damage. Is it distributed throughout the field, or limited to field edges? If the distribution is limited, a border treatment may be sufficient and save money.

A variety of insecticides are labeled on soybeans for control of caterpillars.  See the UNL Entomology website for treatment information.

Bob Wright
Extension Entomologist, Lincoln