Mistaken as worms, caterpillars will certainly destroy privacy trees. The two most common caterpillars are inchworms and tent caterpillars. Both types of caterpillars defoliate trees by feeding on leaves, which will make the trees more susceptible to diseases. Furthermore, the webs of the caterpillars make the trees unattractive, and large colonies cause a hassle for anyone who decides to go outside.
Collect eggs from the leaves of the tree and put them in soapy water. Soapy water prevents the eggs from hatching, and will essentially prevent any caterpillars from raiding your privacy tree.
Wind the webs of the caterpillar's nests onto a stick and place them into soapy water. Web sizes vary according to the sizes of the colonies.
Place bird houses on the trees to promote a welcoming environment for birds. Birds will feed on the caterpillars and reduce their population size.
Spray an insecticide on the trees that contains Bacillus thuringiensis (bt). This product will kill only caterpillars and will not affect the other insects living on the tree.
Spray the insecticide around the area of the tree to ward off any remaining caterpillars. This will prevent any caterpillars from returning the tree, and will allow your tree time to gain its defenses back.
Spray the insecticide on the tree each year around the end of March to prevent any caterpillars from nesting on your privacy trees.