Plant Health Initiative

Green Cloverworm - Scouting

The green cloverworm has 3 pairs of abdominal prolegs Photo credit: Kansas State University

Estimates of soybean defoliation Photo credit: Marlin E. Rice, Iowa State University

Green cloverworm larvae are pale green with two narrow white strips along each side of the body. These white lines become faded when the caterpillars are fully-grown (about one inch long).

The green cloverworm looks similar to the soybean looper, except for the number of prolegs (short legs along the middle of the body). Cloverworms have three pairs of prolegs. Loopers have one or two pairs, and most other soybean-infesting caterpillars have four pairs of abdominal prolegs.

Another unique characteristic used to identify green cloverworm is the tendency of the larvae to wiggle violently when squeezed; no other caterpillar in soybeans exhibits this behavior.

 

Determining Threshold Levels
Many entomologists recommend using leaf defoliation as the best gauge for making management decisions, especially in fields with multiple insect species feeding on the leaves.

Collect the following information during field visits to help determine treatment thresholds

• the average defoliation level for the field
• if the number of larvae present is increasing, decreasing, or appears to be constant
• if diseased and/or parasitized larvae are present
• if other insect defoliators present.

Resources

Estimating soybean defoliation Iowa Integrated Crop Management