early instar gypsy moth caterpillar Pamm Cooper photo

Gypsy moth caterpillar. Note the faint blue spots on the back toward the head, followed by several red dots.

Can you hear the munching? Are the leaves of your trees being eaten? If you are finding hairy, black caterpillars with blue and red spots with a little white thrown in for good measure,  gypsy moth (Lymantria dispar) caterpillars are present. High populations are being found around the state, probably due to the warmer winter which allowed many egg masses to make it through the winter.

Around 500 eggs are laid in buff-colored masses of  during July. Egg masses can be laid on trees, homes, fence posts and just about anywhere the female moth is able to reach. Scrape off any you find, and crush or put in a container of soapy water. Alternative control is to spray mass with horticultural oil. Egg masses not eradicated will over-winter, waiting to hatch during late April into early May. Newly hatched caterpillars spin a fine thread of silk to ‘balloon’, carried by the wind hoping to land on a host plant. Oak trees are their preferred food source, but they will feed on many other plants if opportunity presents.

There are five to six larval stages of the caterpillar. The early stages of the young caterpillar stay in the trees to feed at night, hiding under leaves during the day. Later stage or older caterpillars drop to the ground to find hiding places during the day. This is the stage people notice them congregating under eaves, on houses, tree trunks and other shaded places providing protection from heat and sun, and predators.

gypsy moths on foundation

Gypsy moth caterpillars on foundation.

These caterpillars can be killed by spraying with soapy water or collecting them to put in a bucket of soap and water. Wear gloves as some people are allergic to the hairs along their bodies.The caterpillars climb back up the trees in late afternoon and evening to continue feeding. Banding the trees with burlap coated with a sticky substance such as Tanglefoot or petroleum jelly will catch the caterpillars as they try to climb the trunk to reach the leaves. Daily cleaning of the burlap to remove the stuck caterpillars will keep them off the leafy portion of the tree.

gypsy moth band, uwex.edu

gypsy moth Burlap-band-iwex/edu

By the third week of June until mid July, caterpillars are done feeding. Caterpillars leave the trees to a seek a protected spot to pupate. Pupation lasts about two weeks, then the adult moths emerge. The female moth is whitish with faint brown marks. The male moth is darker brownish. The female cannot fly so the male flies to her to mate. Females then climb up trunks or other objects to lay the egg mass. Adults only live about two weeks and there is only one generation per year.

gypsy_moth_female_and_male Gypsy moth male (left),female (right).

Gypsy moth male and female, (Photo by Lilly Calderon, Kelly Estes) hyg.ipm.illinois.edu


-Carol Quish