Understanding the Threat of Invasive Insects to Pennsylvania’s Forests

The lush forests of Pennsylvania are under threat from a variety of invasive insects, often referred to as “bad bugs.” These pests, which are not native to the region, pose significant risks to the environment, economy, and even human health. Jonathan Geyer, Executive Director of the Pennsylvania Department of Agriculture’s Hardwoods Development Council, emphasizes the importance of public awareness and action in combating these threats. Here, we delve into the specifics of these invasive insects and their impacts on Pennsylvania’s forests.

Gypsy Moth: A Persistent Threat

The gypsy moth is a notorious forest pest responsible for the devastation of millions of oaks and other tree species across Pennsylvania. This invasive insect, originally from Europe, was first identified in the state in 1932. Gypsy moths are easily distinguishable: the females are white and larger, while the males are brown and capable of flight.

Gypsy moths lay egg masses on various surfaces, including trees and stones, with each mass containing 400 to 600 eggs. These eggs hatch in the spring, giving rise to caterpillars that voraciously consume tree leaves, particularly those of oak trees. The process, known as defoliation, can severely weaken trees and lead to their death after repeated infestations.

Gypsy moth populations follow a cyclical pattern, typically peaking every ten years. Wet springs and a naturally occurring soil fungus help control their numbers, but vigilance is still required to manage outbreaks effectively.

Hemlock Woolly Adelgid: A Threat to the State Tree

The eastern hemlock, Pennsylvania’s state tree, is under siege by the hemlock woolly adelgid. This invasive insect, originating from Japan, was first detected in Pennsylvania in the late 1960s. The adelgid feeds on the sap of hemlock trees, depriving them of essential nutrients, which leads to needle loss, branch dieback, and potentially the death of the tree within five to ten years.

The hemlock woolly adelgid is tiny and often goes unnoticed until significant damage has occurred. It creates protective woolly masses at the base of needles on the underside of branches, which serve as its habitat and egg-laying sites. These woolly masses resemble small cotton balls.

Cold winters can slow the spread of this pest, but as Pennsylvania’s winters become milder due to climate change, the adelgid’s impact may worsen, threatening the survival of the eastern hemlock.

Emerald Ash Borer: Destroyer of Ash Trees

The emerald ash borer is another devastating invasive insect, causing extensive damage to Pennsylvania’s ash trees. This metallic green beetle, about half an inch long, is native to Asia and was first discovered in Detroit, Michigan, in 2002. It reached Pennsylvania in 2007 and has since spread to every county, decimating ash tree populations.

Emerald ash borers lay their eggs in the bark of ash trees. The larvae hatch and burrow into the cambium layer, disrupting the tree’s ability to transport water and nutrients. This results in the tree’s death. Historically, ash wood has been used for a variety of products, including furniture, flooring, and baseball bats.

The emerald ash borer’s rapid spread and high mortality rate among ash trees make it one of the most concerning invasive species in Pennsylvania.

Asian Longhorned Beetle: A Potential New Threat

Though not currently established in Pennsylvania, the Asian longhorned beetle poses a significant threat due to its presence in neighboring states. This beetle feeds on a variety of hardwoods, including maple, birch, ash, and poplar. Native to China and Korea, the beetle has been found in Massachusetts, New York, and Ohio, and was eradicated from New Jersey.

The Asian longhorned beetle is identifiable by its shiny black body with white spots and long black and white antennae. The larvae bore into trees, disrupting their vascular system and eventually killing them. Signs of infestation include oozing sap, sawdust buildup, and large exit holes.

Spotted Lanternfly: A Growing Menace

The spotted lanternfly, originally from Southeast Asia, was first detected in Pennsylvania in Berks County in 2014. By 2020, it had spread to 26 counties in Pennsylvania and parts of neighboring states. This invasive insect feeds on the sap of a wide range of plants, including grapevines, hops, and hardwood trees like maple and black walnut.

The lanternfly excretes a sugary substance called honeydew, which promotes mold growth and attracts other insects. The pest goes through several nymph stages before reaching adulthood, each stage posing a threat to plants by feeding on their sap.

Walnut Twig Beetle: Carrier of Thousand Cankers Disease

The walnut twig beetle, native to the southwestern United States, was found in Pennsylvania in 2011. This small beetle, about the size of a pencil tip, carries a fungus that causes thousand cankers disease, which is fatal to walnut trees. The beetle’s larvae tunnel through the bark, introducing the fungus and creating cankers that disrupt the tree’s nutrient flow.

Currently, several counties in Pennsylvania are under quarantine to prevent the spread of this beetle.

Conclusion: Taking Action Against Invasive Insects

Invasive insects pose a serious threat to Pennsylvania’s forests. Public awareness and proactive measures are essential to protect these valuable natural resources. Simple actions, such as not moving firewood long distances and reporting sightings of invasive insects, can make a significant difference. For more information on invasive insects and how to help, visit agriculture.pa.gov or extension.psu.edu.

Together, we can safeguard Pennsylvania’s forests for future generations.