Gypsy moths are invasive insects that can defoliate hundreds of tree species found throughout North America. In Indiana, birches, oaks and poplars are just a few tree species susceptible to gypsy moth damage. While tree mortality is not immediate, after a few years of repeated defoliation, death is nearly inevitable. This is a concern to Indiana’s 4+ million acres of forests as 80% of our trees are preferred by this forest pest.
The gypsy moth was accidentally introduced in the northeastern United States in 1869. In 1972, evidence that the gypsy moth had spread to Indiana was found in Lake County. The moth has kept to the very northeast part of the state - plus Porter County in northwest Indiana - but this may not always be true. Gypsy moths can spread easily when given the opportunity. Egg masses can be found in the cracks and crevices of anything found outside including cars and camping equipment. And though females cannot fly by the weight of the eggs they carry, they can "balloon" their way from one tree to another on a thin thread of silk they produce.
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Whether or not a tree dies following gypsy moth attack depends on its health, the number and severity of prior defoliation and the presence of other pests or fungi that will also attack these already-stressed trees. Although forests affected with a gypsy moth outbreak can and have recovered, it is certain that the forest will be forever changed.
The Gypsy Moth's Stages of Life
The gypsy moth goes through four developmental stages during its life: egg, caterpillar, pupa and adult. Its form and behavior vary greatly as it moves through its life cycle. By recognizing the gypsy moth at each stage, you can help slow the spread throughout Indiana.
Eggs — In August - April, female moths will lay their eggs on any convenient surface with each egg mass containing anywhere between 500 - 1000 eggs. These masses are coated with tan-colored hairs to protect them from the elements and other environmental stresses. If they survive, the eggs will hatch the following spring.
Caterpillars — The caterpillar stage is when the Gypsy moth is most destructive with one caterpillar consuming at least 11 square feet of foliage during its lifetime. Beginning in early April, small black-headed larvae emerge at budbreak of (mostly hardwood) trees hatch and climb to the tops of trees where they begin to feed on foliage. Later they will enter a second stage growth distinguished by irregular shaped yellow markings on their largely black upper body. Older caterpillars have even a more distinct coloring of their backs with five pairs of blue dots followed by six pairs of red dots.
Pupae — Caterpillars stop feeding and transform into pupae (the transition stage between caterpillars and adult moths) by early June. No webs or cocoons for these moths; pupae are enclosed in brown, shell-like cases that are about 2 inches long and sparsely covered with hairs.
Adults — Adults emerge from pupal cases in anywhere between July and August. Females have creamy white wings, tan body and cannot fly. Males are smaller, darker and have feathery antennae. Both have distinct inverted V-shape marks that point to small black dots on their wings.
Gypsy Moth information from Indiana's Department of Natural Resources
Purdue's Extension - Gypsy Moth in Indiana
Gypsy Moth in North America from the US Forest Service
US Department of Agriculture Forest Service - Gypsy Moth