Why Spray Gypsy Moths At All? That's the question MOTHER EARTH NEWS recently asked Dr. Charles F. Wurster, associate professor of Environmental Science at the State University of New York at Stony Brook. And Dr. Wurster graciously provided us with this information about natural and artificial gypsy moth control:
"The gypsy moth situation is what I call an ‘exaggerated insect problem:’ blown all out of proportion. The fact of the matter is, the best thing to do about an infestation of these moths is to ignore it!
"You see, these pests have built up a fair complex of natural enemies since their immigration to America: birds, rodents, other insects, and diseases. So, after an infestation, the trees leaf out again and there usually won't be another large increase in the moths' numbers for several years; their predators will be more numerous following a large gypsy moth hatch, and diseases will have run rampant through the overblown moth population. Spraying, in fact, often is beneficial to the gypsy moth—though it does kill many individual insects—because it thins the pests out enough to prevent any of their diseases from reaching epidemic proportions. Because of this, the year that follows a spraying will typically produce a second outbreak of the pests. Some people, of course, will see this flare-up as reason enough for yet another spraying, and so the cycle goes on.
"Also, since the `early instars'—the moth's larvae—have generally begun to disperse by the time that second spraying is made, there is a strong possibility that the insecticides help to `select' dispersion as a moth characteristic, thereby causing the range of the bugs to spread! The entire American population of these insects, for example, was confined to eastern Massachusetts until the first DDT sprayings of the late '40's and early '50's. That `moth control' may well have been responsible for the dispersal of gypsy moths all over the Northeast, and it's probably how they got to Michigan in the first place!