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Gypsy Moth Control

When do I put tape around the trees to keep the gypsy moths off? Thanks, Lynne

The gypsy moth was introduced into the United States by a French scientist living in Massachusetts. The native silk spinning caterpillars were proving to be susceptible to disease so he brought the gypsy moths into this country in an attempt to make a disease resistant hybrid. When some of the moths escaped from his lab, they grew to be one of the
most notorious pests of hardwood trees in the Eastern United States. Over 75 million acres of trees have been defoliated since 1970.

They feed on several hundred different species of trees and shrubs but oaks and aspens are their favorites. Some of the highest concentrations of the Gypsy Moth are in the southern Appalachian Mountains, the Ozark Mountains and in the northern Lake states.

How you choose to combat this pest depends on where it is in its life cycle. The eggs hatch in early spring through mid-May at about the time when most trees are budding out. Natural dispersal occurs when the newly hatched, tiny
larvae hang from the host tree on silken threads. They are so small and light that they can float quite a distance in
a strong wind. During this dispersal a lot will fall to the ground. This is the stage when you should wrap tree trunks with sticky bands to prevent larvae from crawling up to the foliage. If the bark on your tree is furrowed, put aluminum foil or other stuffing between band and trunk so they cannot crawl beneath it. If the bands lose their adhesion use a product such as Tangletrap to resurface the bands. Any larvae less than 1/2 inch long may be sprayed with BT, but it is not very effective on the larger larvae.

If the larvae make it up the tree, they will remain there for the first 3 or 4 molts (called instars) feeding on the
leaves. Each molt increases the size of the caterpillar, which goes on to eat more leaves.

In early summer, when the caterpillar reaches the fourth molt it will begin a daily migration up and down the trunk
seeking shade to rest in during the day. At this point you need to change your pest control strategy. Remove the
sticky bands as they are mostly useful for young larvae. Tie 18 inch wide burlap bands around the tree. Fold the
top of the band over the bottom to create a flap. The larvae will crawl into the shade between the layers of burlap
where you can easily pick and destroy them. Drop them into soapy water or just snip them in half with scissors.

In a year when populations are heavy, the caterpillars do not migrate. Instead they remain in the branches and feed
continuously. I guess they’re afraid of not getting their share. If they completely strip the tree, they will crawl
elsewhere looking for more food.

During this stage, they will molt two more times. In mid-summer they will enter the pupal stage for a couple of
weeks, emerge as moths, mate and the female will lay creamy white egg masses covered with yellow hairs. The moths die
after mating and the winter is spent in the egg stage.

There are pheromone traps that can be used in mid to late summer when the moths emerge and the males fly during the
afternoons looking for a female to mate with. However, most of the species of females cannot fly and remain close to the area where they emerged from the pupae.

Late fall and early spring is the time to search out and destroy egg masses. You can find these egg masses on the
underside of tree limbs, bark, rocks, or any structure, but most will be on the tree trunks. When collecting them to
destroy, look for pinholes on the eggs. These are evidence that they have been parasitized with by a natural predator. Hold off removing and destroying them until after the first hard frost to allow this beneficial insect to build up its numbers. When the temperature is above 40 degrees, spray egg masses with oil spray to kill them.

Alternatively you can collect them in a cup and microwave them on high for 2 minutes, cover them with soapy water for
2 days, scrape them into a jar of alcohol, burn them. Throw the remains in the trash.

Birds are also helpful in the battle against the gypsy moth. Chickadees and nuthatches will peck at the egg masses and some species of birds with longer beaks will feed on the caterpillars, but generally they can’t eat enough to bring a population under control. Most birds won’t touch them because of the extensive hairs on the older larvae.

Deer mice and shrews are the biggest predator of larger caterpillars and ants are the biggest predator of the tiny,
young larvae.