It has a native range that extends over Europe and parts of Africa, and is an invasive species in North America.

For regulatory purposes, the U. S. Department of Agriculture has defined Asian Gypsy Moth as "any biotype of Lymantria dispar (sensu lato) possessing female flight capability".

[1] In North America in July 2021, the Entomological Society of America announced it was delisting the common name gypsy moth as part of an effort to replace racist or otherwise offensive names, as Gypsy is considered an offensive slur by some in the North American Romani community.

One states that despite issuing oral and written warnings of possible consequences, no officials were willing to assist in searching out and destroying the moths.

[6]: 10  The other notes that Trouvelot was, in fact, well aware of the risk and there is no direct evidence that he contacted any government officials about the moths' release.

[6]: 10  The first major outbreak occurred in 1889, and Forbush and Fernald recount the extent of devastation: all the trees being defoliated and caterpillars covering houses and sidewalks and raining down upon residents.

[6]: 1, 10  At first it was uncertain what species was responsible for the outbreak, but after the caterpillar was identified by entomologist Maria Elizabeth Fernald, an eradication program began in 1890.

[5]: 1 [13] Eventually they would reach the Pacific Northwest, sporadically invading but so far not becoming established there, due to successful eradication campaigns.

[6]: 10  According to the United States Department of Agriculture, without intervention, this pest spreads about 13 miles (21 km) per year.

[15] A study published in 2012 suggests that storms can accelerate the spread, hypothesizing that strong easterly winds carried larvae across Lake Michigan to Wisconsin, a distance of at least 50 miles (80 km).

[17][18] Egg masses are typically laid on branches and trunks of trees, but may be found in any sheltered location, including rocks, foliage and vehicles.

[6]: 13  The larvae will disperse even if there is enough foliage for growth, hanging from silk threads and waiting for the wind to send them aloft.

[6]: 12  The female has a small gland near the tip of the abdomen that releases the pheromone with a pumping motion, termed "calling".

The eggs are covered with a peachy fuzz that can cause serious rashes if touched by bare skin or fur.

[25] The gypsy moth brings one of the largest impacts in defoliation of deciduous trees in the Northern Hemisphere.

[26] The gypsy moth avoids ash trees, tulip-tree, American sycamore, butternut, black walnut, catalpa, flowering dogwood, balsam fir, arborvitae, American holly, and mountain laurel and rhododendron shrubs, but will feed on these in late instars when densities are extremely high.

Some species, such as the white-footed mouse or Anastatus disparis, have a significant impact on the population dynamics of the moth.

The white-footed mouse, Peromyscus leucopus, is considered important for regulating sparse moth populations.

[6]: 21  The white-footed mouse is the most common and widely distributed small mammal in the northeastern United States.

[6]: 108 Insectivorous birds prey upon the larva of the gypsy moth, but the egg clusters are protected by their hair coverings.

[6]: 21  The effects of bird predation have not been fully studied in North America,[6]: 21  but it has been well documented in Japan and Eurasia.

[6]: 105  Birds that consume gypsy moth larvae, pupae and adults include the blue jay, red-eyed vireo, eastern towhee, northern oriole, catbird and the European robin.

[6]: 21  In low density populations, there is a positive correlation between larval mortality and predation rates on pupae.

[27] The population in Austria suffered high parasitism by the tachinids Parasetigena silvestris, which may have contributed in prevention of further increase in L. dispar in this locality.

The most important pathogen is the Lymantria dispar multicapsid nuclear polyhedrosis virus (LdMNPV), sometimes referred to as NPV or Borralinivirus reprimens.

Temperatures of −9 °C (16 °F) can be withstood during the winter, an extended period will kill the larvae inside and −23 °C (−9 °F) even for a short time is lethal.

[6]: 23 Disparlure has been synthesized artificially and has been used to confuse mating patterns or lead male moths into traps.

However, this technique is less successful against concentrated populations, hence its main use may be to delay infestation until other ecological solutions are found.

[21] Forest defoliation by the gypsy moths each year affects the populations and reproductive success of forest-dwelling birds.

[36] In coastal Maine and Cape Cod, Massachusetts, caterpillar-triggered rash is much more likely due to exposure to brown-tail moth (Euproctis chrysorrhoea).