The Final Gypsy Moth Management Plan/Environmental Assessment
is now available online.

The Gypsy Moth and the Environment
The gypsy moth (Lymantria dispar) is the most obvious and widespread defoliating insect of hardwoods in the northeastern United States. An exotic insect from Europe, the moth has spread southward from Maine to Virginia, Pennsylvania, and west into Ohio. Limited infestations have occurred in Michigan, Wisconsin, and even Utah.

Gypsy moth larvae (caterpillars) are voracious defoliators. The larvae can feed on over 500 species of trees, shrubs and vines. The gypsy moth most favorite tree species are the oaks, which are a significant component of Cuyahoga Valley forests. Other favorites found in the park include river birch, hawthorn, and willow. Moderately desirable species that can be defoliated include cherry, cottonwood, elm, blackgum, hickory, hornbeam, maple, and sassafras.

Defoliation directly affects trees by decreasing their health and vigor. This can result in an increased susceptibility to disease and parasites, leading to increased tree mortality. Defoliation and the loss of mature trees can change forest and understory composition, water quality in streams and lakes, and quality and availability of food for terrestrial and aquatic wildlife. This can result in changes in the abundance and distribution of wildlife. Since the gypsy moth is a non-native species, its effects on the environment are not part of natural ecological processes and are therefore largely undesirable.

Gypsy moths also present aesthetic, safety, and health concerns to employees and the public. Large stands of defoliated or dead trees can impact scenic values and present hazardous tree conditions. Large numbers of caterpillars and their frass (droppings) can be a nuisance, affecting outdoor recreational experiences. Forest fire hazard levels can be increased with defoliation and tree mortality. Some individuals that are exposed to the hairs on gypsy moth larvae may develop skin rashes or irritations and allergies.

Monitoring Gypsy Moths in Cuyahoga Valley National Park
Park managers began a gypsy moth monitoring program in 1987 with the placement of pheromone traps at over 200 sites using a 1/2-mile grid across the park. These traps contain a pheromone strip that attracts flying male moths and a small insecticide strip. Traps are useful tools for monitoring low-level moth populations and detecting new populations. The number of moths caught in traps was generally low until the mid-1990s when numbers started increasing. The use of traps was discontinued after the summer of 1998, as the number of moths trapped became uniformly high and traps became less useful for monitoring.

In 1990, the park sponsored a workshop to discuss the expected gypsy moth problem. Participants included NPS staff from parks already impacted by the moths, other agency representatives, and community representatives. At that time, park managers determined that the park would not pursue active gypsy moth management. There were hopes that the fungus Entomophaga maimaiga (Em), which infects and kills gypsy moth larvae, might control the moth population as has apparently occurred in the eastern US in recent years. The fungus is known to be present in and around the park.

Since 1996, the Forest Service has conducted aerial surveys of the park to quantify gypsy moth defoliation. Within the boundaries of the park, moderate to heavy defoliation was detected that covered approximately 39 acres in 1996, 54 acres in 1997, and 175 acres in 1998.

Unfortunately, natural controls failed to suppress gypsy moth populations in 1999. A large gypsy moth outbreak occurred, resulting in 4,372 acres of defoliation in the park. In response to the serious defoliation that occurred that year, 575 egg mass survey plots were assessed in the fall of 1999 to document the status of gypsy moth populations in susceptible park forests. The egg mass survey indicated that much of the park was at risk for severe defoliation impacts in the spring of 2000.

Gypsy Moth Suppression Begins
The park completed and issued an Environmental Assessment in the spring of 2000 which prescribed gypsy moth suppression in critical areas of the park using aerial applications of biological insecticides. In May 2000, approximately 6,300 acres of forested federal land were treated with two applications of Bacillus thuringiensis variety kurstaki (Btk) and 800 acres were treated with two applications of Gypchek®. Btk is a bacterial insecticide that affects the larvae of the gypsy moth and some other butterfly and moth species. Gypchek® is a virus-based insecticide that affects only gypsy moth larvae. There are no known adverse effects on people or pets from the aerial application of these pesticides.

After the pesticide treatments, aerial surveys conducted by the Forest Service in July 2000 recorded approximately 404 acres of defoliation in the park. Suppression was effective in 99.8% of treatment areas on federal land. It is believed that natural controls such as the Em fungus contributed to gypsy moth control efforts.

Gypsy moth egg mass surveys were conducted in November 2000 to help gauge the status of gypsy moth populations across the park. Results of the survey indicated that only a small area of the park, totaling approximately 400 acres, was at risk for defoliation in 2001. The park treated this area with Btk in May 2001.

Current Status of Gypsy Moths
No defoliation occurred within or near the park in 2001, nor have detectable levels of the moth been present since. Gypsy moth populations have been reduced to almost immeasurable levels in the Cuyahoga Valley area. It is likely that populations will remain low for some time, but the moth is not eradicated and could eventually become a problem again under certain circumstances. The park continues to work with the U.S. Forest Service to monitor populations so that future outbreaks will be identified early.

Future Management of Gypsy Moths
The park issued a Gypsy Moth Management Plan/Environmental Assessment for Cuyahoga Valley National Park in January 2001. This document analyzes potential gypsy moth management alternatives and outlines the decision-making process for determining when suppression of gypsy moth populations in the park is warranted in future years. The full document is available.

After public review of a draft document that examined several gypsy moth suppression program alternatives, the alternative that prescribed suppression of gypsy moth populations in a set of Gypsy Moth Management Areas was selected. These areas include forested areas that have been previously defoliated, areas of significant recreational value, and buffer zones adjacent to non-federal treatment areas. Suppression would involve aerial application with one of the two aforementioned biological insecticides, Btk and/or Gypchek®.

The decision regarding which, if any, of these areas would be sprayed each year will be based on a set of criteria including defoliation risk, tree mortality risk, the history of previous treatments, and the presence of sensitive areas. The total area sprayed will fluctuate annually in response to changes in gypsy moth population levels and defoliation effects as documented by an annual monitoring program. The park will continue coordination efforts with other federal, state, and local agencies and notify the public of any park spray plans each year.