Some insects can be removed simply by picking them off by hand or by pruning infected branches. Not at all. The gypsy moth, for example, originally introduced from Europe to the U.S. East Coast, is spreading westward after wreaking havoc in urban and other forests along the eastern seaboard. The gypsy moth was named for its propensity to travel, often hitching rides from humans. The moth may lay its eggs on the underside of a camper or lawn furniture, and when the camper travels from state to state, the eggs go too.
Few trees are immune, with only tuliptrees, sycamores and ginkgos resistant to the bug.
Its attacks can be fatal if factors such as drought or stress exist in the victim trees. This devastating variety apparently arrived in Vancouver in the past year or so on a ship from Siberia. More threatening than its European cousin, the Asian moth feeds on more than 500 species of trees, and it devastates conifers, the economic mainstay of the Pacific Northwest. In April, a Bt spraying program began in Washington, Oregon, and British Columbia. A lesser problem is the tussock moth, which is hitting evergreen and horse chestnuts, particularly in the Midwest.