University of Illinois Extension


The larva or caterpillar is the damaging stage as it eats the leavesof trees in the spring. They can consume tremendous amounts of leafmaterial. For example, Gypsy moth larvae can consume as much asone square foot of leaves per day. As a result, they produce a largeamount of fecal (frass) material. When populations reach outbreakproportions, the caterpillars can completely defoliate host treesover a wide geographic area. Consistent or repeated defoliationover several years can have devastating effects, often leading totree stress and death.

Gypsy moth damage

Gypsy moth damage

Gypsy moths have a wide host-range, which includes oak (Quercus sp.), crabapple (Malus sp.), linden (Tilia sp.),poplar (Populus sp.), beech (Fagus sp.), willow (Salix sp.), birch (Betula sp.), sweetgum (Liquidambar styraciflua), serviceberry (Amelanchier sp.), and hawthorn (Crataegus sp.). Trees less susceptible to attack by Gypsy moth are ash(Fraxinus sp.), sycamore (Platanus sp.), Indian bean(Catalpa sp.), honeylocust (Gleditsia sp.), dogwood(Cornus sp.), junipers (Juniperus sp.), yew (Taxus sp.), lilac (Syringa sp.), arborvitae (Thuja sp.),arrowwood (Viburnum sp.), and tulip tree (Liriodendrontulipifera).

Conifers are more susceptible to death than evergreens becausethey don't produce another flush of growth once defoliated. Conifers,such as pine (Pinus sp.) and spruce (Picea sp.), areunable to produce new leaves (needles) after defoliation as comparedto deciduous trees. As a result, conifers can die after one severedefoliation.

The ecological and economic impact of Gypsy moth is a serious concern.Gypsy moth defoliation can change the complexity of understory growththus resulting in an increase or decrease of certain fauna or flora.Consecutive defoliation can result in plant stress and possibledeath. Gypsy moth defoliation may predispose trees to attack byopportunistic insects or diseases. For example, Gypsy moth feedingcan increase a tree's susceptibility to the attack by the shoestringfungus, Armillariella mellea and the two-lined chestnut borer, Agrilus bilineatus. In forested neighborhoods and urban parks,dead trees are a safety hazard. Large numbers of caterpillars area nuisance and the hairs may cause skin and/or respiratory allergies.In addition, the fecal droppings can cover large areas and makeit difficult to enjoy outdoor activities such as barbecues, swimming,and picnics. In fact, reduced attendance in recreational areas and/orresorts may occur during outbreaks.

This site is for use by municipal forestry departments, park districts, the green industry and other concerned agencies to report gypsy moth findings in Northeastern Illinois. The site will be monitored by University of Illinois Extension staff and the Illinois Department of Agriculture to assist in the effort to suppress the spread of gypsy moth.