[Image: Fall Webworm]Fall webworms are being reported at this time in many pecan and shade trees. The adult fall webworm is a medium-sized white moth with a stout body. The forewings are sometimes marked with brownish to black spots.
Two races of fall webworm are recognized in Louisiana. Larvae (caterpillars) of the orange race have orange heads and tuberacles. The larvae are covered with long, silky hairs that arise from the tubercles. Full grown are 1 to 1 ¼ inches long. In the south, pecan, hickory, persimmon and sweetgum are the preferred hosts.
The black race, generally more prevalent in southern Louisiana, has four generations each year, the first beginning in late March and the larvae of the last pupating in early November.
The insects overwinter in the pupal stage in leaf litter and the surface layers of the soil. Moths are active during the summer and early fall. After mating, the females lay their eggs in masses on the underside of leaves. Larvae hatch in about a week and feed in groups. As they grow, they construct large, loose, irregular, silk webs, which cover leaves, twigs and small branches. As the larvae need food, the webs are enlarged to enclose more leaves. When ready to pupate, they leave the webs and find protected places such as bark crevices or, for the last generation of the year, the soil.
Type of Injury:
The large, ugly webs of the fall webworm seriously detract from the beauty of shade trees. Defoliation caused by the larvae feeding on pecan leaves can reduce the quality of the current season’s nuts, and if defoliation is extensive, reduce crop yields the following season. Fall webworms do not attack the nuts and will not kill a tree outright. However, massive defoliation over several years may weaken a tree making it susceptible to damage by other insects and diseases.
In residential areas, it is one of the most important pecan pests, because homeowners rarely have the type of spray equipment required to adequately cover large pecan trees and supply enough pressure to penetrate the webs.
When only a few webs are involved on small trees, it is more economical to prune them from the trees. Periodic inspection will allow for removal of the webs before they become large, numerous and unsightly. If the homeowner chooses to spray, several insecticides safe for use in residential areas are available which give satisfactory control of the fall webworm. For the insecticides to use and the proper rates to apply, contact the LSU AgCenter Extension Office.
Now, for a horticulture hint on sweet potatoes.
Dig sweet potatoes before a frost occurs. Cure potatoes after digging by storing 85 to 90 degrees F and 85 percent to 90 percent humidity for four to seven days. Cured potatoes will keep longer, since the skinned and bruised areas are allowed to heal over. After curing, hold potoates at about 60 degrees F with a high humidity. Maximum sweetness will be obtained six to seven weeks after harvest. Do not store sweet potatoes in the refrigerator. Dust potatoes kept for seed with 5 percent Imidan for weevil control.