Gypsy Moth

Invasive species with origins in Europe, Asian and Africa. Consumes significant portion of hardwood tree leaves in the eastern United States. 80.4 million acres of defoliation from 1970 to 2010.

Latin Name

Lymantria dispar dispar

Trees Affected

Oaks, aspens, grey birch, basswood/linden, mountain ash, Lombardy poplar, willows, witch-hazel, beech, red cedar, chestnut, hemlock, plum, pine, and Colorado blue spruce

Threat to Trees



Consistent defoliation over a number of years can lead to mortality, especially when paired with other diseases and pests in susceptible species and trees. One year of heavy defoliation (>51%) in hemlock, pine and spruce can lead to mortality, and 2 or more years of defoliation in deciduous trees may lead to mortality. “A normal outbreak pattern includes 2 years of light infestation with minimal defoliation followed by two years of moderate to severe defoliation with population collapse after the second year of heavy defoliation (PSU).”

Signs & Symptoms

Heavy defoliation causing stress to host plants. Evidence of wood-boring pests and root-rot may also indicate Gypsy Moth infestation.


Egg masses are deposited by females during July on trees, hatching in April and May. Larvae remain on host plants and feed during the day, eventually feeding at night as adults. Adults emerge in late June.

Domestic Origins

Boston, MA, 1869

Geographic Location

New England, eastern New York, New Jersey

Photo Credits