Masking tape girdles many trees in Southwestern Ontario. It seems the gypsy moth caterpillars are particularly abundant this year. According to many authorities, such as the experts at the University of Wisconsin/Madison, used correctly, bands of tape can reduce the number of caterpillars attacking residential trees.
The university claims homeowners can reduce the number of gypsy moth caterpillars in invading a homeowner's trees by putting up barrier bands of masking tape before the caterpillars start to hatch in mid-May. Caterpillars crawling up the trees get mired down in the tape bands coated with petroleum jelly and die. The bands also keep caterpillars from migrating to other trees or from climbing back up if they fall off the tree (surprisingly common!).