Publication E-78
January 1979
Purdue University
Cooperative Extension Service
West Lafayette, Indiana 47907

The Green Cloverworm on Soybeans
C. Richard Edwards and David L. Matthew, Extension Entomologists
The green cloverworm is a periodic pest of soybeans in several midwestern states including Indiana. In 1968 and 1973 several thousand acres of soybeans were treated for control of this pest. Outbreaks of lesser magnitude occurred in 1975 and 1977. Since the green cloverworm is a defoliator, the damage appears very serious. This damage does not always result in reduced yields, and control treatments are often applied when not actually needed. With today’s increasing cost of production, the additional cost of $4 to $6 per acre for unnecessary sprays is mighty expensive "insurance." To help you make the right pest management decisions, the following discussion includes a detailed description of the green cloverworm, its life cycle, and a treatment chart that provides guidelines to show when it is profitable to treat for green cloverworm.

Description and Life Cycle of the Adult Green Cloverworm
Adult green cloverworms are dark brown to black, medium-sized moths with a wing span of about 1-1/4 inches. Their bodies are about 1/2 inch long. Their antennae are 3/8 inch long and thread-like. A narrow projection from the front of their heads gives them a distinctive snout-like appearance.
When at rest, the moths are triangular shaped. During the day the moths hide on the underside of leaves and on the walls of houses and sheds where their color enables them to rest unnoticed. However, at dusk they become quite active and quickly fly off if disturbed. Their flights generally cover only a short distance before the moths quickly alight again. Adult moths feed on nectar and, on warm evenings, can be seen flitting from plant to plant in a zigzag, up and down fashion.
On the average, adult green cloverworms live 7 to 16 days and female moths lay 150 to 200 eggs. The eggs hatch in 2 to 5 days during warm weather; however, when temperatures are cool, eggs may take up to 2 weeks to hatch. Hibernating moths do not follow the typical life cycle. They usually hide in barns, fencerows, woodlands and other places which provide protection from predators and harsh winter temperatures.

The Larval and Pupal Stages
Newly-hatched green cloverworm larvae are pale yellow to light green. As the larvae grow, they assume the color of their host plant, blending in with their surroundings, except for the two white stripes which run the entire length of their bodies. (For a picture of a green cloverworm larva see Extension Publication E-85.) The early larval instars tend to skeletonize the underside of soybean leaves, leaving the upper epidermis intact. However, as the larvae grow, they consume all but the major veins of the leaf. This type of feeding gives the plant a ragged, hail-damaged appearance. The larvae will molt 5 times and complete their development in 3 to 4 weeks. One larva consumes about 7 to 8 square inches of foliage during its development. When fully grown, the larvae usually crawl to the ground and pupate either in plant refuse covering the ground or slightly below the soil surface. The pupal stage lasts 7 to 24 days, except when the pupa is the overwintering stage. Adult moths emerge quite early in the spring in extreme southern Indiana, usually as soon as host plants such as clover and alfalfa begin to grow. There are 2 to 3 generations of the green cloverworm per year in Indiana.