There are many types of caterpillars that attack mature trees by eating their leaves and defoliating them. The repeated defoliation of a mature tree places it under significant stress and makes the tree more vulnerable to other diseases or aggressive insects such as boring insects, which can cause mortality.
At the first sign of caterpillars on the tree, spray with Garden Insect Spray with Spinosad or Bug Buster Pyrethrin Insect Spray and repeat the spray every two to three weeks, until the feeding period has ended. In the fall, remove any visible egg nests or spray them with Horticultural Oil Insect Spray. In the spring, place a sticky TreeHelp Bug Bandon the trunk of the tree to prevent the caterpillars from migrating from the ground up towards the tree’s leaves.
In the early spring, treat trees that are too tall to spray with Once-A-Year Insecticidal Drench w/Merit, to provide insect protection throughout the growing season.