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Green Cloverworm

Authors: Scott D. Stewart, Angela McClure and Russ Patrick

Classification and Description:  The adult green cloverworm (Plathypena scabra) is a moth in the family Noctuidae.  The moths vary in appearance but are triangular shaped when at rest and about 5/8-inch long. Males are bigger than females and are charcoal gray.  Female moths also have a charcoal color with patches of brown and silver.  Both sexes of moths have labial palps which point forward from the head to make a distinctive “snout”.  Eggs are laid singly or in small groups.  Larvae are about 1-inch long when full grown.  They are pale green with a white stripe down the length of each side of the body.  They are identified by having four pairs of abdominal prolegs (one pair at the tip of the abdomen and three additional pairs).  Thus, they can be readily distinguished from loopers which have three pair of prolegs. The pupae are brown and found in a lightly wrapped silken cocoon.

Hosts, Life History, and Distribution:  The green cloverworm is native and is most commonly found in the eastern United States.  Larvae feed on a wide variety of legumes.  Cloverworms overwinter near the Gulf Coast and migrate northward each spring.  At least three generations per year are possible in Tennessee.  It takes about 25-28 days for an individual to develop from egg to adult.

 

Pest Status and Injury:  In Tennessee, green cloverworms occasionally cause economic damage to soybean by feeding on leaves.  Excessive defoliation can indirectly impact yield by reducing the amount of photosynthate produced by leaves for seed development.  It is unusual for green cloverworms to cause economic damage unto themselves, but infestations often coincide with other defoliating pests such as soybean and cabbage loopers.

 

Management Considerations:  Beneficial insects and diseases normally keep populations of green cloverworm larvae below economically damaging levels.  When necessary, larvae are relatively easy to kill with insecticides.  Insecticide recommendations are listed in the Tennessee Insect Control Recommendations for Field Crops (PB 1768).  Treatments are prescribed when larvae threaten premature defoliation. Soybeans are most susceptible to defoliation during peak pod filling (stages R1-R6).  Defoliation thresholds vary from 20-30% depending upon the stage of crop development.  Typically, it takes about 150 green cloverworms per 100 sweeps to cause greater than 20% defoliation.  Once fields reach physiological maturity (R8), they are less susceptible to defoliation and insecticide treatment is probably not justified.

Reference: Handbook of Soybean Insect Pests, L. G. Higley and D. J. Boethel (eds.), Entomological Society of America, 1994.

Printer Friendly PDF File: Green Cloverworm (W198)