Gypsy moth

Type Description

"The male Gypsy Moth is brown with darker brown markings on its wings. Females are slightly larger and almost white, with a few dark markings on their wings. Newly hatched caterpillars are black and hairy, later developing a pattern from yellow to gray with clusters of hair-like tufts and two rows of blue then red spots on their backs (Walker, 2005).

While adult females of Asian strains can fly, those of European strains cannot. Larvae of Asian strains are also larger. The North American population is of European origin. Due to these differences, eradication efforts are typically more aggressive during attacks by Asian strains (Walker, 2005). The ability of female Asian Gypsy Moths to fly long distances (up to 20 miles) enables them to rapidly invade and spread in the United States. In contrast, the spread of the European Gypsy Moth to the Northeast has taken over 130 years (since 1869). In the East, European strains defoliate an average of 4 million acres of trees each year, causing millions of dollars in damage (APHIS 2003)."

Habitat

"It is found in natural forests, coastal areas, and urban areas.

Native Range: Lymantria dispar is native to Europe, northern Africa, central and southern Asia, and Japan (Martin 2000).
Known Invasion Range: The European species has been introduced to the United States and Canada and is now present in much of northeastern North America, with its range expanding southward and westward.
In Turkey, it has been detected in the Eastern Anatolia Region (Bayramoğlu et al. 2017), the Istrian Mountains (Georgiev et al. 2012), Trabzon, Samsun, Yozgat (Gencer et al. 2018; Demir et al. 2012), Erzurum (Çoruh & Özbek, 2005).

Natural Clothing/Boots: Caterpillars adhere to travelers and their belongings.
Natural Dispersal (Local): Late instar larvae can crawl up to 100 meters. Late instar caterpillars climb to the tops of host trees, where the wind can carry them to other trees. Young larvae have hairs that can catch small pockets of air, allowing them to be carried for kilometers when the wind is strong."

Reproductive Information

"Mating begins with females releasing a sex pheromone from abdominal glands that attracts males. Mating lasts for about 30 minutes, and females deposit their eggs within 24 hours after mating. Males are polygynous, but females mate only once with a single male, as releasing pheromones for multiple matings cannot occur.

Adults reproduce once a year, typically in July or August. Females usually lay about 1000 eggs per breeding season, often on the trunks and branches of trees. While development of the larvae inside the eggs takes only about a month, they typically do not hatch for 8 or 9 months. They spend most of their lives in the tree canopies, often in a silk web near or on the host tree, until they reach the pupal stage. Overall, they reach sexual maturity in about 11 months."

Lifecycle

This species has four stages in its metamorphic life cycle: egg, larva, pupa, and adult. Eggs are laid on tree trunks or branches in July or August. After 4 to 6 weeks, the embryos hatch into larvae. These larvae enter diapause as eggs over the winter and emerge from the eggs in the spring of the following year according to the budding cycles of the trees on which they are laid. L. dispar typically undergoes five or six instar stages before reaching the pupal stage. The pupal stage typically lasts 7 to 14 days. After eclosion, males emerge 1 to 2 days before females. Mating occurs after adult females emerge, followed by egg deposition. Both individuals die after laying eggs, and the cycle repeats (McManus et al., 1989).

Nutrition Information

Hatching larvae typically begin feeding on expanding buds and then move on to newly expanded leaves. High populations often result in the defoliation of a large spatial area of trees.

General Impact Information

"Lymantria dispar primarily feeds on the leaves of deciduous trees. In most regions and most years, it remains at low densities and does not cause noticeable damage. However, sometimes populations reach high densities, and these outbreak populations can completely defoliate host trees.

The most significant impacts of Lymantria dispar, especially if they occur over several consecutive years or in conjunction with drought, are associated with the physiological stress on trees due to leaf loss. These effects include decreased tree growth, crown dieback, and tree mortality. Tree mortality is often associated with other insects (wood borers) and pathogenic fungi attacking stressed trees. In extreme cases, approximately 100% tree mortality can occur over large areas. The most significant effects occur in urban environments.

Outbreaks typically last 1 to 5 years. Outbreak populations then decline due to starvation and increased disease. Small mammalian predators are considered the most important source of mortality in low-density populations and can keep sparse populations of the next outbreak in check for several years. Leaf defoliation by Lymantria dispar can lead to poor regeneration by reducing tree seed production and root sprouting.

In the larval stage, Lymantria dispar can feed on more than 500 different tree and shrub species. Preferred hosts in North America include oak, cherry, birch, maple, red oak, willow, black oak, and trembling aspen. The Asian strain is also invasive on coniferous trees such as fir and has a broader host range than the European strain (Humble and Stewart 1994). It is estimated that over 30 million hectares of forest in the United States have been defoliated since 1970 (de Beurs and Townsend 2008). In Canada, the spread of Lymantria dispar northward and westward has been prevented so far by climatic barriers. However, current climate change predictions are expected to increase the climatic suitability range for Lymantria dispar (Regniere et al. 2009). Similar warming trends are also emerging in climate prediction models for Lymantria dispar in the western United States."

General Management Information

"Preventive Measures: Forests can be managed to prevent outbreaks. High-risk forests can be harvested before outbreaks occur to mitigate some economic losses. Thinning to remove high-risk stands can increase the vitality of surviving trees and reduce the risk of major outbreaks. Thinning to reduce the ratio of primary Gypsy Moth hosts can also reduce the frequency and intensity of leaf drop.

In New Zealand, legislation and quarantine procedures may require ships coming from areas with Gypsy Moth populations to undergo ""high-risk"" inspections for egg masses located up to eight kilometers offshore before entering the harbor. If found, the ship is directed to a 20 nautical mile boundary for cleaning before continuing to the high-risk inspection once again eight kilometers offshore (Dijkhuis, 2005).

Spread Prediction: One of the challenges in managing biological invasions is the lack of reliable methods to predict and forecast the spread of an introduced species. Therefore, developing effective spread predictions for invasive species is a priority concern for management programs. Tobin et al. (2007) used county-level presence/absence quarantine records and detailed pheromone trap data from the Slow Spread program to predict the spread of Gypsy Moth. The STS pheromone trap data were spatially extensive and evenly spaced due to a network of over 100,000 traps placed on the transition zone between infected and uninfected areas (Tobin et al. 2004, Tobin et al. 2007).

Peterson et al. (2007) conducted ecological niche modeling using climate data from the natural range of Asian Lymantria dispar. This showed that ecological niche data from the Asian strain could relatively accurately predict the geographic distribution of better-known European L. dispar populations, indicating that the ecological characteristics of the two strains are very similar. The ecological niche model suggests that both Asian and European Gypsy Moth strains have the potential to colonize almost all temperate regions except mountainous areas and deserts (Peterson et al. 2007). However, control of the Asian population is more difficult due to its faster maturation and better dispersal abilities (Peterson et al. 2007; Barnachikov 1989).

Monitoring Impact: Despite efforts to prevent the continuous spread of Gypsy Moth, the affected area of North American forests continues to expand. As the invaded area increases, ecological, environmental, and economic concerns remain significant. Moderate Resolution Imaging Spectroradiometer (MODIS) is an important tool for large-scale detection of leaf drop by L. dispar."

General Pathway Information

"Unintentional Transport: Egg masses of Lymantria dispar can be inadvertently transported. Egg masses of Lymantria dispar are tolerant to extreme temperatures and humidity, and they travel well on logs, lawn furniture, nursery stock, pallets, shipping containers, and the hulls and equipment of ships (APHIS, 2003).

Caterpillars adhere to travelers and their belongings. In this way, they can hitch rides and travel continentally."

Notes

The species does not have a reported field of use in the literature.

References