The larva or caterpillar is the damaging stage as it eats the leaves
of trees in the spring. They can consume tremendous amounts of leaf
material. For example, Gypsy moth larvae can consume as much as
one square foot of leaves per day. As a result, they produce a large
amount of fecal (frass) material. When populations reach outbreak
proportions, the caterpillars can completely defoliate host trees
over a wide geographic area. Consistent or repeated defoliation
over several years can have devastating effects, often leading to
tree stress and death.
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 (Liriodendron
Conifers are more susceptible to death than evergreens because
they don't produce another flush of growth once defoliated. Conifers,
such as pine (Pinus sp.) and spruce (Picea sp.), are
unable to produce new leaves (needles) after defoliation as compared
to deciduous trees. As a result, conifers can die after one severe
The ecological and economic impact of Gypsy moth is a serious concern.
Gypsy moth defoliation can change the complexity of understory growth
thus resulting in an increase or decrease of certain fauna or flora.
Consecutive defoliation can result in plant stress and possible
death. Gypsy moth defoliation may predispose trees to attack by
opportunistic insects or diseases. For example, Gypsy moth feeding
can increase a tree's susceptibility to the attack by the shoestring
fungus, 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 are
a nuisance and the hairs may cause skin and/or respiratory allergies.
In addition, the fecal droppings can cover large areas and make
it difficult to enjoy outdoor activities such as barbecues, swimming,
and picnics. In fact, reduced attendance in recreational areas and/or
resorts may occur during outbreaks.