Newly hatched gypsy moth caterpillars float through the air on silken strands and travel in hordes from plant to plant, often defoliating entire trees. While some trees can recover from such infestations, many--including most conifers--cannot. The pests pupate during the summer in the same trees they infested as caterpillars. They mate as flying adult moths; the pregnant females then become so heavy that they must crawl rather than fly into nearby trees to lay their eggs.
Control gypsy moths by handpicking the chamoislike egg masses and caterpillars. Wrap tree trunks with sticky barriers to keep female moths from climbing up to lay eggs. Assassin bugs, spined soldier bugs, parasitic wasps, and tachinid flies will parasitize caterpillars and kill them. A special Bt strain, Bt kurstaki, will kill caterpillars while they are still small.
Chemical controls such as acephate or carbaryl will control larger, more mature caterpillars, but be aware that these will also kill the pests' natural enemies.