Green Cloverworm in Soybean
Published: 04/10/2026
Crop Damage
The green cloverworm (Hypena scabra) occurs in Mexico, across the Atlantic Coast, and westward to the Great Plains in the United States, as well as in eastern Canadian provinces. Early instars feed on soft leaf tissue in the upper one-third to one-half of the soybean canopy. Feeding results in a tattered appearance, with only the midrib and major veins remaining. Under heavy infestations, larvae can cause significant defoliation and may feed on pods once leaf tissue is depleted.
Green cloverworm defoliation.
Ashley Dean, Iowa State University
Pest Description
Full-grown larvae are approximately 1½ inches long and pale green, with distinct longitudinal white stripes. A key diagnostic feature is the presence of three pairs of prolegs on the abdominal segments and one pair at the terminal end, distinguishing them from other soybean defoliators. Adults are brown moths with a characteristic “snout.” Females typically have silver wing markings, whereas males are more uniformly charcoal in color.
Green cloverworm. Orange arrows indicate characteristic prolegs.
Adam Sisson, Iowa State University
Scouting and Management
Moth arrival and population development vary by region and seasonal conditions. Pheromone trap networks, where available, can help determine when to initiate scouting. Three primary sampling methods are recommended:
Sweep net: Conduct 20 sweeps at five or more locations across the field. The treatment threshold is approximately 150 larvae per 100 sweeps.
Drop cloth: At 10 locations, place a 6-foot sheet between rows and shake plants to dislodge larvae. Record the average number of larvae per row foot. The treatment threshold is when there are more than 15 larvae per row foot.
Defoliation estimates: Randomly sample plants throughout the field to estimate whole-plant defoliation. The Crop Protection Network’s Insect Defoliation Tool can assist with accurate estimation. The treatment threshold is 30% defoliation during vegetative stages and 20% during reproductive stages.
When evaluating populations, note the presence of parasitized larvae or fungal infections, as natural enemies often suppress green cloverworm populations below economic thresholds. For current sampling recommendations and management options, consult your local extension specialist.
Developed and reviewed by Carol Pilcher, Iowa State University and Robert Wright, University of Nebraska-Lincoln, with support from the United Soybean Board.
Green cloverworm. Adam Sisson, Iowa State University.
Green cloverworm defoliation. Ashley Dean, Iowa State University.
Orange arrows indicate characteristic prolegs. Adam Sisson, Iowa State University.
Green cloverworm adult. Orange arrow indicates distinct snout. Mark Dreiling
Gallery images courtesy of Adam Sisson, Iowa State University; Ashley Dean, Iowa State University; and Mark Dreiling, Bugwood.org.
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