If you have a canker worm infestation you can apply chemicals- but you have to catch the infestation early. The best time to spray pesticides on your trees is when the canker worms are still young (less than a half-inch long), two weeks after they’ve hatched. It can be difficult to detect this before it’s too late. This is usually in the first two weeks of April- but timing is everything.
By the time we typically notice canker worms (when they dangle from the trees and get caught in our hair) it’s too late to spray for canker worms. Charlotte's city arborist is watching for the signs of hatching and will decide, on a yearly basis, if spraying will be helpful.
Of course, the best way to manage an infestation is to prevent it by using tree bands. In fact, Charlotte has a very active tree banding program in place, to keep our tree canopy healthy and beautiful.