Plant Health Initiative

Green Cloverworm - Agronomic Impact

Leaf damage due to feeding by green cloverworm larvae. Photo credit: Kansas State University

Although common in soybean fields, especially in the southern states, green cloverworm is generally not considered a serious pest.

Young larvae feed on soybean leaves and skeletonize the underside of the leaf. Older larvae eat all of the leaf except large veins. Green cloverworms feed mainly on the top third of the plant, giving the impression of extensive damage long before economic damage has occurred.

Thresholds
Reductions in yield from insect feeding can occur during any crop stage, but the pod-forming and pod-filling stages are the most sensitive.

In general, consider treatment of soybean only if leaf-feeding insects are present and defoliation reaches 20% in the pod-forming and pod-filling stages.

The economic threshold during the vegetative stage is much higher, generally 35-40% or in some cases even 50-60%. According to Marlin Rice, at Iowa State University, a 40% leaf loss during any vegetative stage will result in only a 3-7 percent yield reduction. Defoliation of 20% during the pod-forming and pod-filling stages will result in similar yield reductions.