Issues In Choosing An Insecticide For Gypsy Moths
We do not recommend using any insecticides for gypsy moth control unless the life of the tree or shrub is threatened. At this time, a biological pesticide known as Bacillus_thuringiensis or “Bt,” has the least toxic impact on other life forms such as beneficial insects and birds.

The decision to use any insecticide to control gypsy moths depends on the condition of the trees or shrubs you want to protect. If they are healthy and vigorous they may not need spraying. If, however, they do need to be sprayed, you can treat small trees and shrubs with a backpack_sprayer. For small trees and shrubs up to 15 feet tall you will need a trombone sprayer.

Larger trees should be treated by a professional arborist who will have the proper equipment and expertise. For example, a 30-foot tree will require about 10 to 20 gallons of spray material for effective control. This is best done by a trained applicator.

What Not To Do If Tree Is Defoliated
If the tree has been defoliated then there should be no crown thinning by arborists or fertilizing by anyone for at least two years after the last defoliation. Both these practices were common among tree professionals but have since been shown to be very harmful and stressful to the tree under attack.