Green cloverworms in alfalfa and soybeans

There are not a lot of soybeans grown on the southern High Plains, but we've seen high numbers of green clover worms causing serious damage this week. Soybeans in Crosby County were sprayed the other day, and Blayne Reed (CEA-IPM, Floyd, Swisher, Hale counties) reports similar high numbers in Floyd county as well.

The following was written by Dr. Pat Porter, Texas A&M Agrilife Extension Entomologist, and posted on the FOCUS on Entomology blog.


If you are growing soybeans or alfalfa on the Texas High Plains, it would be a good idea to scout for green cloverworms. I was in a soybean field near Ralls earlier in the week that had approximately 8 larvae per plant, and I just got a call about soybeans near Clarendon that were heavily infested.

In both cases the people making the reports thought the worms were soybean loopers. It is easy to tell the two caterpillars apart because loopers have two pairs of prolegs on the abdomen while the green cloverworm has three pairs. Loopers are fairly lethargic, but green cloverworms hop around quickly when disturbed.

Green cloverworm larvae near Ralls

Typical defoliation in soybean caused by green cloverworm

Fortunately the green cloverworm is only a leaf feeder in soybean and it does not damage pods. For alfalfa here is a quote from the Oklahoma guide, "These defoliators are rarely a significant problem in established alfalfa, although seedling stands can be heavily damaged by their feeding." However, if there are enough of them present they can cause defoliation, which in turn will reduce the amount of nutrients the plants can store for overwintering.

For soybeans, University of Tennessee has a good list of insecticides in their publication here. Oklahoma State University has control suggestions for alfalfa here.