Webworms are damaging alfalfa in Nebraska, says Bob Wright, University of Nebraska (UNL) entomologist based in Lincoln. One case has been reported in southeastern Nebraska, another in the northeast. Webworms have also damaged soybeans in central Nebraska, near Curtis. Several species of the pest, including the garden webworm, can damage alfalfa and soybeans. UNL entomologists don't yet know which species is damaging Nebraska's crops.
Several generations of garden webworms develop each season, the last of which may overwinter in soil in the pupa stage. Larvae feed on a wide variety of plants, including alfalfa, clovers, beans, soybeans, sugar beets, and corn. Feeding causes leaf surfaces to take on a brown, netted appearance as green matter is stripped, leaving only the network of leaf veins to dry and curl inside the webbing.
The best control method in alfalfa is to harvest the crop, if possible. Kan-sas State University entomologists suggest that treatment may be needed in alfalfa if significant defoliation involves 25-30% of terminals. A variety of foliar insecticides should control webworms. Visit entomology.unl.edu/fldcrops/pestipm.shtml for a list of insecticides labeled for use in alfalfa and soybeans.
Source: University of Nebraska.