Gypsy Moth -- Control

A single defoliation seldom kills a hardwood tree. Loss of one-half of the tree's foliage results in little more than a reduction in growth. However, when most of the foliage is lost, the tree doesn't have the ability to produce growth. Stored food in roots are at the lowest. The plant has difficulty producing additional leaves to compensate for those lost. The tree's effort to re-foliate itself in the summer strains the root system and usually results in twig, branch and bud death during the winter. If Gypsy Moths defoliated plants in the fall, few trees would be lost. Repeated loss of leaves over consecutive years usually spells the end of the tree. A single defoliation of a conifer, however, can result in tree death.

Tree death can occur following a single year defoliation if the specimen is suffering drought stress or is on a poor site.

Many trees don't succumb directly due to defoliation but by secondary invaders that attach the weakened tree. These can include other insects, diseases or environmental conditions such as drought or floods that can cause fatal injury.

Efforts should be made to keep affected and unaffected trees in a healthy state. Affected trees should receive adequate mulching, watering and fertilizing to help them recover. Judicious pruning might reduce stress on the plant. Planting of less susceptible tree species should also be encouraged.

The major source of Gypsy Moth disbursement in the United States is through motor vehicles. A vehicle and plant materials from Gypsy Moth infested areas should be checked thoroughly for any signs of the insects including egg, larva, pupae and adults. Visual inspection may involve examinations of a vehicle's underside, joints or hitches. Both sides of wheels should be checked.

Control is difficult and controversial. Chemical control is effective but requires community support and action. Community-wide spraying usually runs into opposition and is costly.

Egg masses should be removed and placed in cans of rubbing alcohol, bleach or kerosene to prevent hatching. Just scraping eggs off the trees and onto the ground does not reduce the population significantly. Most chemicals painted on egg masses have little effect on the masses and can damage the cambium layer of the tree. Banding trunks with substances such as Tangle-Foot seem to have little control on infested trees. Some success can be achieved on sprayed or non- infested plants. Contact the Illinois Department of Agriculture (IDA) before controlling any of the stages.

Chemical control in Illinois is on the advice and assistance of the Illinois Department of Agriculture.

The Illinois Department of Agriculture annually conducts survey of Gypsy Moth activity using phermore traps. Visual surveying of egg masses also provide information on potential outbreaks.

If any Gypsy Moth egg masses, caterpillars or moths are found, notify the Illinois Department of Agriculture immediately.

See: Gypsy Moth--Identification; Gypsy Moth--Hosts

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