1. Invasive Species In Pennsylvania
A look at three species posing an increasing threat to biodiversity in the state.

2. Terms to Know
Non-Native Species: Species introduced or spread from one region of the US to another outside their normal range
Introduced Species: A species established outside of its natural range due to human activities or interventions.
Invasive Species: An introduced species that increases in abundance at the expense of native species.
Exotic Species: A species that occurs outside its natural range due to human activity.
Richard B. Primack. Essentials of Conservation Biology. 4th Edition. Sinauer Associates Inc

3. Why should we be concerned?
The introduction of organisms to ecosystems where they are not normally found can have dramatic results.
Invasive species can have both economic and ecological impacts that are often nearly impossible to reverse.
The following slides will discuss a cross section of the many invasive species that are currently found in Pennsylvania as well as many other states.

4. Purple Loosestrife (Lythrum salicaria) Natural History
Purple loosestrife was introduced to the northeastern U.S. and Canada in the 1800s, for ornamental and medicinal uses.
Many states now have regulations that prohibit its sale, purchase and distribution.

5. Purple Loosestrife Habitat Preference
According to the U.S. Fish and Wildlife Service, purple loosestrife now occurs in every state except Florida.
Purple loosestrife is capable of invading many wetland types, including freshwater wet meadows, tidal and non-tidal marshes, river and stream banks, pond edges, reservoirs, and ditches.
Photos: Agriculture and Agri-Food Canada Archives, Agriculture and Agri-Food Canada,

6. Purple Loosestrife Ecological Threat
Purple loosestrife adapts readily to natural and disturbed wetlands. As it establishes and expands, it outcompetes and replaces native grasses, sedges, and other flowering plants that provide a higher quality source of nutrition for wildlife.
The highly invasive nature of purple loosestrife allows it to form dense, homogeneous stands that restrict native wetland plant species and reduce habitat for waterfowl.

7. Purple Loosestrife Economic Threat
An estimated 190,000 hectares of wetlands, marshes, pastures and riparian meadows are affected in North America each year, with an economic impact of millions of dollars.
Purple loosestrife also invades drier sites. Concern is increasing as the plant becomes more common on agricultural land, encroaching on farmers’ crops and pasture land.

8. Purple Loosestrife Treatments
Controlling the spread of purple loosestrife is crucial to protecting vital fish, wildlife and native plant habitat!
Biological Control: Galerucella pusilla and G. calmariensis are leaf-eating beetles which seriously affect growth and seed production by feeding on the leaves and new shoot growth of purple loosestrife plants.
Physical Control: Where infestation is
limited, pulling up plants by hand can be effective.

9. Zebra Mussels (Dreissena polymorpha) Natural History
Zebra mussels are native to eastern Europe and western Asia in the Black, Azov, and Caspian Sea drainages.
Zebra mussels first appeared in the Great Lakes in Lake St. Clair in 1988, and shortly there after Lake Erie.
The mussels were likely transported to the Great Lakes in the ballast water of ships.

10. Zebra Mussels Habitat Preference
Confirmed zebra mussel occurrences.
Zebra mussels are found mainly on hard substrates, such as rock, wood, concrete, and steel.
They are rarely found at depths greater than 50 feet.
Mussels can survive out of water for up to five days, making it easy for them to be carried from lake to lake on recreational boating and fishing gear.

11. Zebra Mussels Ecological Threat
Zebra mussels are efficient filter feeders, capable of straining one liter of water per day to consume plankton. This removal of plankton, in turn, reduces the amount of food available for other organisms.
Zebra mussels, which like to colonize on hard surfaces, can also kill native mussels and clams by using their tough byssal threads to build thick colonies over them, hindering their ability to feed.

12. Zebra Mussels Economic Threat
Zebra mussels attach themselves in large clumps on hard surfaces such as boat hulls, docks, and buoys.
Each year the economic impact to the United States and Canada is about $140 million in damage and control costs.

13. Zebra Mussels Treatment
To prevent the spread of zebra mussels to new locations boaters are asked to drain all water and ensure no mussels “hitch a ride” to new bodies of water.
Small areas, such as clogged pipes, can be cleaned with hot water (140°F or above).
In Pennsylvania, it is unlawful to possess, sell, purchase or transport zebra mussels.

14. Marmorated Stink Bugs (Halyomorpha halys) Natural History
Marmorated Stink Bugs were first collected in the U.S. in September of 1998 in Allentown, PA - but probably arrived several years earlier.
This true bug in the insect family Pentatomidae is known as an agricultural pest in its native range of China, Japan, Korea and Taiwan.
Stink bugs are a serious pest of fruit, vegetables and farm crops.

15. Marmorated Stink Bugs Habitat Preference
This insect is becoming an important agricultural pest in Pennsylvania.
In 2010, it produced severe losses in some apple and peach orchards.
It also has been found feeding on blackberry, sweet corn, field corn and soybeans. 
In neighboring states it has been observed damaging tomatoes, lima beans and green peppers.

16. Marmorated Stink Bugs Ecological Threat
Feeding on tree fruits such as apple results in a characteristic distortion referred to as “cat facing,” that renders the fruit unmarketable as a fresh product.
Unfortunately, since this is a nonnative pest, there are few currently known biological controls within the United States.

17. Marmorated Stink Bugs Economic Threat
Mid-Atlantic apple growers lost $37 million last year from damage caused by the brown marmorated stink bug.
Some fruit growers in Pennsylvania have lost 40 to 50 percent of their crops to stink bugs.
Stink bugs do their damage by inserting mouthparts under the skin of the fruit, injecting saliva and sucking out the juices.

18. Marmorated Stink Bugs (Treatment)
Inside homes the most common remedy has been to drown the bug in soapy water or simply vacuum them up.
Rutgers University has investigated use of black lights as well as green and yellow traps with an aggregate pheromone to attract the brown marmorated stink bug.

19. Work Cited
DCNR Invasive Exotic Plant Tutorial for Natural Land Managers. Accessed 1/23/12:
Richard B. Primack. Essentials of Conservation Biology. 4th Edition. Sinauer Associates Inc
Minnesota Sea Grant. Purple Loosestrife: What you should know, what you can do. Accessed January 26, 2012 at:
Pennsylvania Sea Grant. Zebra and Quagga Mussels. Accessed January 26, 2012 at:
Penn State University. Brown Marmorated Stink Bug. Accessed January 30, 2012 at:
Stanton Gill, et. al. Brown Marmorated Stink Bug. IPM Pest Alert. October University of Maryland Extension. Accessed January 30, 2012 at: