The 5 Most Destructive Invaders Taking Over Pennsylvania in 2026

Here are the five most destructive invaders currently waging war on the Keystone State this year.

1. The Spotted Lanternfly: The Agricultural Assassin

Now entering its second decade in the United States, the Spotted Lanternfly (SLF) remains Pennsylvania's most notorious resident. By early 2026, the state-imposed quarantine had expanded to cover 56 of Pennsylvania's 67 counties.

• The Threat: This "hitchhiker" insect feeds on over 70 different plant species. It is a direct threat to Pennsylvania's $132 million grape industry, as well as apples, hops, and hardwoods.
• The "Honeydew" Problem: As they feed, they excrete a sticky substance called honeydew. This attracts stinging insects and fuels the growth of "sooty mold," which blackens garden furniture, patio decks, and entire forest understories, killing the plants beneath.
• 2026 Outlook: While populations have dipped in the original "ground zero" counties of the southeast, they are surging in Western and Northern Pennsylvania as they follow transportation corridors.

2. Hemlock Woolly Adelgid: The State Tree Executioner

The fate of the Eastern Hemlock, Pennsylvania's state tree, hangs in the balance in 2026. This tiny, aphid-like insect from Asia has officially been confirmed in all 67 counties, leaving no corner of the state untouched.

• The Damage: The adelgid settles at the base of hemlock needles and sucks the life-sustaining sap. Without intervention, a healthy, centuries-old hemlock can be killed in less than a decade.
• The Riparian Risk: Hemlocks are "foundation species" that shade cold-water streams. Their loss leads to rising water temperatures, which threaten Pennsylvania's native Brook Trout populations.

3. Spongy Moth: The Canopy Consumer

Formerly known as the Gypsy Moth, the Spongy Moth has returned with a vengeance. Following significant outbreaks between 2021 and 2025, 2026 is shaping up to be another heavy defoliation year for Pennsylvania's oak-dominated forests.

• The Impact: During peak summer, millions of caterpillars can strip an entire mountainside of its leaves in days. While a healthy tree can survive one defoliation, repeated attacks—coupled with 2026's unseasonably dry spells—lead to massive "oak die-offs."
• Economic Toll: The loss of timber value and the cost of aerial spraying programs represent a significant drain on state forestry budgets.

4. Asian Jumping Worms: The "Brazen" Soil Saboteurs

Gaining "brazen" status in 2026 due to their aggressive expansion into suburban gardens, the Asian Jumping Worm is a relatively new and terrifying threat to Pennsylvania's soil health.

• Identifying Behavior: Unlike docile European earthworms, these thrash violently like snakes when touched and can even leap into the air.
• The "Coffee Ground" Effect: They consume the organic "duff" layer of the forest floor at twice the rate of native worms, leaving behind a dry, granular soil that resembles coffee grounds. This soil cannot hold moisture or nutrients, effectively preventing new oak and maple seedlings from ever taking root.

5. Northern Snakehead: The "Frankenfish" Predator

The Northern Snakehead solidified its presence in the Susquehanna and Delaware River basins in 2026. This predatory fish is often called the "Frankenfish" because of its primitive lungs and ability to survive on land.

• The Incursion: In late 2025, reproduction was confirmed in new sections of the Lower Susquehanna. These fish can "crawl" short distances across wet land to move between ponds and streams, making them incredibly difficult to contain.
• The Ecological Chaos: They are apex predators that eat everything from native bass and trout to frogs, small birds, and even rodents. They outcompete Pennsylvania's prized game fish for both food and territory.

How You Can Fight Back in 2026

The spread of these invaders is primarily driven by human movement. You can help protect the state by following these "Active Defense" rules:

1. Don't Move Firewood: This is the primary way the Lanternfly and Spongy Moth reach new counties. Buy it where you burn it.
2. Scrape and Squash: Winter is the time to identify Spotted Lanternfly egg masses (which look like gray mud smears) on trees and vehicles. Scrape them into a bag of rubbing alcohol.
3. Kill on Sight: If you catch a Northern Snakehead, Pennsylvania law requires that you do not release it. Kill the fish immediately and report the location to the Fish and Boat Commission.
4. Check Your Plants: Before planting a new garden this spring, inspect the soil for jumping worms. If the soil looks like coffee grounds, do not move those plants to your property.