Invasive Species in York County
Present problems, Future threats

Invasive Insects | Invasive Plants | Aquatic Invasive Species | Photo Credits | Contacts

Many of us already know that non-native invasive species such as gypsy moth and mile-a-minute cause both ecological and economic damage. For example, York county parks and landowners are currently feeling the effects of the latest gypsy moth infestation cycle. Pathogens like West Nile Virus along with its non-native mosquito vectors affect both human health and quality of life. These invaders are now established and breeding and the only option is management. Pennsylvania considers this issue important enough to have an Invasive Species Management Plan and have established the Pennsylvania Invasive Species Council web site. For information on national efforts to control invasive species, visit the National Invasive Species Information Center. To appreciate the borderless nature of the problem, visit the Global Invasive Species Team web site.

There are many other invasive animal, plant, insect and disease problems hovering near York County. Because of short travel times and tourism, particularly during the summer months, county residents and park personnel need to be aware of these potentially destructive ‘visitors’. The best chance for eliminating an invasive species locally occurs when the organism is newly arrived but not yet fully established. Early detection combined with a rapid response for removal are critical. All of us are potentially part of the problem and must be part of the solution.

Some of the important species of concern in Pennsylvania and likely to cause economic or environmental damage or both are listed here.

Featured Pests:

Invasive Insects

Emerald Ash Borer (Agrillus planipennis)

Native to: China and Eastern Asia, probably arrived in wood packing
Already present in western Pennsylvania counties, EAB has recently been reported in Mifflin county. Because EAB is hard to detect and has no good control options as yet, Pennsylvania Department of Agriculture has placed these counties under quarantine. The quarantine restricts the movement of ash green nursery stock, green lumber and any other ash material, including logs, stumps, roots and branches. All hardwood firewood is also quarantined due to the difficulty of distinguishing between species and the ability of larvae and eggs to hide under bark.

Adults are one-half inch long and one-eighth inch wide, metallic green, and fly only from mid-May through September, primarily during June and July. The larvae spend the rest of the year under the bark of the trees feeding until they emerge as adults through an one-eighth inch "D" shaped hole. EAB attacks all species of ash in the genus Fraxinus, including green, white, and black ash but not Mountain Ash. Infested trees typically die within four years, regardless of age, vigor or species.

Signs of ash decline that may be caused by EAB or some other stressors include: upper crown dieback, yellow foliage or small branches coming directly out of the trunk, woodpecker damage. Signs specific to EAB include: adult beetles, D-shaped exit holes, flat-headed caterpillars (larvae) and S-shaped galleries under bark.

The DCNR Bureau of Forestry is conducting surveillance, but a homeowner reported the Mifflin infestation. If you see EAB, report it to PA Department of Agriculture 1-866-253-7189, or Penn State Cooperative Extension

For more information on Emerald Ash Borer:

Emerald Ash Borer
PA Department of Conservation and Natural Resources Emerald Ash Borer

Asian Longhorned Beetle (Anoplophora glabripennis)

It is established in Massachusetts, New York, New Jersey
Native to: China and Korea, entered the country in untreated solid wood packing materials.
Asian Longhorned Beetle is a large (0.75 - 1.5 inch), glossy jet black, very smooth with up to 20 white spots on its back. It has antennae with distinctive black and white banding that are 1 1/2 to 2 1/2 times as long as it's body. Eggs are laid in dime-sized oval grooves chewed into the tree bark. Adult beetles are evident in mid to late summer. Infestations usually start in the crown of the trees and may not be detected until advanced. Signs of tree decline that may be caused by ALB or some other stressors include: upper crown dieback, yellow foliage or small branches coming directly out of the trunk. Signs specific to ALB include: adult beetles, large (3/8"), round exit holes, oozing sap, coarse sawdust at the base of the tree or where branches meet other branches.

The Problem – ALB is a very destructive wood boring beetle that prefers maple trees, but is also known to infest alders, birches, elms, horsechestnut, poplars and willows. There is no effective control other than removing and finely chipping infested trees.

For more information on Asian Longhorned Beetle:

ALB Northeast Survey and Outreach Project
Common look alikes are the Whitespotted Sawyer and the Cottonwood Borer.
US Forest Service Asian Long-horned Beetle Information

For more information on important insect pests in Pennsylvania:

Brown Marmorated Stinkbug
Elongate Hemlock Scale
Hemlock Wooly Adelgid
Important Insect and Disease Pests of Pennsylvania' Forests

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Invasive Plants

Mentioned here is a short list of the plant species causing habitat loss for native plants and animals. Some invasive plants were imported and planted for erosion control or as ornamentals before their detrimental effects were fully realized, some came in as 'hitchhikers' with the movement of people and goods. They can also be spread through hiking and camping activity. Birds and other animals also spread seeds as fruit passes through their digestive systems and on coats, spreading them within a region once they arrive in a new area.

The major problem with all of the invasive plant species is their lack of any natural controls, aggressive growth patterns and rapid reproduction. Combined with their lack of nutritional and habitat quality for native wildlife, they are very disruptive in the forest and watershed ecosystems on which we all depend. In our mid-Atlantic region, find out more at: Plant Invaders of Mid-Atlantic Natural Areas.

Already in the county:

Japanese stilt grass (Microstegium vimineum)
Mile-a-minute vine (Polygonum perfoliatum)
Japanese barberry (Berberis thunbergii)
Privets (Ligustrum spp.)
Exotic bush and vine honeysuckles (Lonicera spp.)

On our border:
Wavyleaf basketgrass (Oplismenus hirtellus ssp. undulatifolius)

For additional information:

DCNR Invasive Exotic Plant Tutorial
Invasive Plants in Pennsylvania
Mid Atlantic Ecological Landscapes Partnership
Penn State Integrated Plant Management Publications
Weeds Gone Wild - Fact sheets and information on control by species
Penn State Natural Resources Extension - Fact sheets on invasive plant and insect species

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Aquatic Invasive Species

The many aquatic invasive species are spread primarily through human activities. Awareness and education among anglers, boaters and other water recreation participants as well as water garden and aquarium hobbyists are vital to limit their spread.

Zebra mussels (Dreissena polymorpha) and Quagga mussels (Dreissena rostriformis bugensis)

Native to: Eurasia
Established throughout most of the northeast and in Pennsylvania
The Problem: These fresh water mussels colonize hard surfaces including native animals, intake pipes, locks and dams, beaches and ship hulls. They are highly efficient filter feeders, removing phytoplankton from the water and starving other water animals. This disrupts the food web in aquatic systems. Human health risks arise from concentration of contaminants in the mussels that further increase in fish feeding on the mussels and in anglers consuming the fish. Economic costs come from clogging intake pipes of water and power facilities as well as damage to boat propellers, hulls and fouling infrastructure like locks and dams.

Northern Snakehead (Channa argus)

Reported: Maryland, Delaware River in Pennsylvania in scattered locations
The Problem: These predators can potentially devastate native fish and wildlife populations. Young snakeheads eat zooplankton, insect and fish larvae and small crustaceans. Frogs, fish, crustaceans, small reptiles even small birds and mammals are taken by adults. Nicknamed “frankenfish,” they tolerate poor water conditions and can move over land for short distances. They are well established in the Potomac River.

Snakeheads: The Newest Aquatic Invader
USGS Channa argus Fact Sheet

Didymo or Rock Snot (Didymosphenia geminata)

Native to: Northern Europe, northwestern North America
Established in western states and in the Delaware River
The Problem: Didymo, a freshwater alga, is primarily spread by anglers, boaters and their equipment but can also be spread on clothing of children or pets wading in an infested stream. It grows in stream beds on rocks creating clumps of stalk material up to 8 inches deep that carpet the bottom, disrupting the stream ecology.

USDA Didymo Species Profile

Hydrilla (Hydrilla verticillata)

Established in the northeast and parts of Pennsylvania
Native to: Asia
The Problem: Hydrilla is a federal noxious weed that grows quickly, forms dense mats and interferes with navigation and irrigation and clogs hydroelectric water intakes. The dense mats prevent sunlight penetration, shading desirable plants growing underneath. It slows the flow of water in streams and irrigation ditches and can be found in freshwater lakes, ponds, rivers, canals and impoundments.

European Water Chestnut (Trapa natans)

Established in the northeast and a problem in the Chesapeake Bay Watershed.
Native to: Europe
The Problem: Dense floating mats choke waterways, limiting light and oxygen and outcompeting native organisms for nutrients and space. It forms sharp nuts that can puncture shoes causing painful wounds and the mats make boating and swimming nearly impossible.

For more information on aquatic invasive species:

Aquatic Nuisance Species (ANS) Taskforce
Habitattitude
Invasive Aquatic Plants: What Every Plant Enthusiast Needs to Know
Pennsylvania Fish & Boat Commission Aquatic Invasive Species
Pennsylvania Sea Grant Aquatic Invasive Species
Protect Your Waters
USGS Nonindigenous Aquatic Species (NAS) Site

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Photo Credits:

If you have questions, please contact:

Tim Abbey, Invasive insects
Connie Schmotzer, Invasive plants
Diane Oleson, Forest pests, Aquatic invasive species
Tom Smith, West Nile Virus, Mosquito surveillance

Penn State Cooperative Extension in York County
112 Pleasant Acres Road
York, PA 17402
(717) 840-7408