When should the trees be banded to control this pest?
Gypsy Moth caterpillars feed on foliage during the day. They make a daily trek from the canopy of the tree to escape predators and direct sunlight.
Eggs are deposited in bark crevices. Appearing in June and July, females in larval form are about 1″ long growing to be 2 1/2 inch long hairy, gray brown caterpillars with red and blue dots. If you band the trees with sticky traps in May and leave them on til end of July, this should interrupt their travel.
To control them:
When larvae are young, spray with BT (Bacillus thuringiensis), repeating every 10-14 days.
After banding the tree, destroy the egg masses and pupae by scraping them off with a putty knife and dispose of them in a container of hot water, household bleach, or ammonia.
For additional information please see the following: http://www.toronto.ca/trees/pdfs/factsheets/European_Gypsy_Moth.pdf