By: Jean Ferdinandsen, Certified Arborist WI-0149A
Once gypsy moth populations reach outbreak levels, the potential for damage and demands for the pest to be reduced increase. Many areas of southeast Wisconsin are now at outbreak levels. Gypsy moth cannot be completely eliminated from an area, even with spraying. However, the population can be reduced to a level where the stress on trees and people are tolerable. The overall goal of control is to keep trees 85% in leaf. In some situations this will require two sprays. We want to reduce the caterpillar population early while they are small, relatively easy to control, and before significant feeding damage is done to your trees.
Some companies promote combining various insecticides at once for control. There is nothing to be gained from these combinations or “cocktails.” In fact, this applies unnecessary materials into the environment and should be avoided.
The Certified Arborists at Wachtel Tree Science and Service can best evaluate control needs and recommend appropriate gypsy moth control strategies. We will use the least toxic materials possible for controls based on sound science.
Gypsy moth management integrates a variety of control tactics and focuses on the egg mass and caterpillar stages. The pupa and adult do not do any feeding damage.
Small caterpillars, those in the first and second instar stages, are controlled with Bt (Bacillus thuringiensis). This bacterial insecticide must be eaten by the larvae to have any effect, and takes about one week to kill them. Bt is effective only on lepidoptera larvae present at that time. It has no effects on people, animals, birds, or non-lepidoptera insects. It is naturally occurring in the soil and degrades when exposed to sunlight.
As the caterpillars get large, Bt is no longer effective. Insecticides that disrupt molting can be used for the first through third instar stages. Then, contact insecticides such as permethrins are used until pupation. While gypsy moth caterpillars may not kill trees by themselves, trees weakened by heavy defoliation may become susceptible to drought, disease, or other insect attacks. Healthy trees may tolerate or resist these secondary attacks, while trees that are in poor health are at higher risk. Keeping trees healthy is the first line of defense against gypsy moths.
Wachtel Tree Science and Service has the knowledge, people, and ability to help keep your trees healthy and deal with gypsy moths in the best and most appropriate manner. Call a leader—call Wachtel.
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