Invaders TitleNYSM home


Global commerce began centuries ago. From food to technology and everything in between, most of us depend upon international trade every day. The world’s oceans used to be a formidable barrier to the dispersal of plants and animals.
Airplanes and large oceangoing ships, however, have increased the potential for non-native species to emigrate to new areas. Modern machines also provide faster modes of transport. Unfortunately, this increases an organism’s chance of survival while in transit.


One way non-native species are introduced to a new area is in solid-wood packing material used for shipping. When trees are cut down to make packing crates or pallets, the pests living in them are transported around the globe. Another common method is through ship ballast water. When ships carry little or no cargo, ballast water provides the ship with the desired draft and stability to make a safe journey. When the ship arrives to pick up cargo, the ballast water and everything in it is pumped out. Although there are limited regulations in place regarding international trade and ballast water, these regulations are inadequate. This makes fighting the entry of non-native species a difficult task.

Zebra Mussel
One of the best characteristics to identify these mussels is the presence of byssal threads. These thread-like filaments enable them to attach to any hard surface underwater. (Gina Mikel,

These mussels clog pipes and raw water conduits within municipal and industrial facilities. The damage and increased operating expenses total hundreds of millions of dollars per year.

Plant growth
Zebra and Quagga Mussels are filter f eeders. When they filter out and eat microscopic algae, water becomes clearer. As a result, there is an increase in the depth that sunlight can penetrate toward the bottom.

Plants then start to grow from the bottom where they did not previously. This causes an ecosystem change. (NOAA, Great Lakes Environmental Research Laboratory)

Zebra Mussel

Dreissena polymorpha

Quagga Mussel

Dreissena rostriformis bugensis
These fouling mussels cause considerable economic and ecological damage. They are regarded as one of the most notorious biological invaders ever to enter North America and are often cited as the “poster child” of aquatic invasive species. The Zebra Mussel is native to the freshwater regions of the Black, Caspian, and Azov Seas and their tributaries. The Quagga Mussel is native to the Dnieper River delta in the Ukraine. They were first detected, respectively, in the Great Lakes in 1988 and 1991. Both probably were initially introduced in ship ballast water. They are present in all the Great Lakes and many of the waterways and water bodies in that region.

Both species have recently invaded California and other western states and will continue to invade new water bodies throughout North America. They are primarily transported by “hitchhiking” on barges and pleasure boats.

There is accumulating evidence that the presence of these mussels in some way contributes to the death of water birds by increasing the presence of botulism toxin in the food web. There are also effects on recreational activities, such as swimmers cutting their feet on mussel shells. Following a storm, these mussels can also be found covering beaches with sharpedged shells and rotting mussel flesh.

Round Goby
Center for Great Lakes and Aquatic Sciences,

Round Goby

Neogobius melanostomus
Round Goby is native to eastern Europe, specifically the Black and Caspian Sea regions, and arrived in ship ballast water. It quickly expanded its range throughout the Great Lakes region since it was first reported in the St. Clair River in 1990. Several characteristics make this species an ideal invader. It grows quickly, produces a large number of eggs, has a breeding season of several months, can spawn several times each year, and feeds opportunistically.

The effects of the Round Goby’s rapid expansion remain unknown. It competes with native species for spawning habitat. It also preys on darters, other small fish, and possibly lake trout eggs and fry. Researchers throughout the Northeast are assessing the effect of this species on native fauna. They also monitor its expansion and examine its effect on the health of other species and the environment.
Asian Long-horned Beetle
Dean Morewood,

Asian Long-horned Beetle

Anoplophora glabripennis
Native to eastern Asia, this beetle was first detected in 1996 in Brooklyn, New York, and downtown Chicago. It was accidentally introduced via wood packing material from Asia. The introduction of this beetle is of great concern. It poses a high risk to the urban and natural forests of New York and elsewhere.

Asian Long-horned Beetle infestations cause the mortality of many hardwood deciduous tree species. This includes maples, elms, poplar, horse chestnuts, and willows. Signs of infestation include tree crown dieback, frass in strands, and large exit holes. On their own, the beetles do not spread quickly. Humans, however, can easily hasten the spread of an infestation. Because beetle larvae live inside trees, people can unknowingly move them great distances in firewood, live trees, or fallen timber.

There are no known predators or diseases of these beetles in North America that would keep their populations in check in their native range. Dealing with problems of invasive species can be costly. Over 18,300 infested trees and trees at high risk for infestation have been cut down and destroyed in an attempt to eradicate the beetle from New York. These measures aim to limit the size of the infested area. Whether or not these efforts succeed remains to be seen.
Emerald Ash Borer

Emerald Ash Borer
Both Emerald Ash Borer photos by David Cappaert, Michigan State University

Emerald Ash Borer

Agrilus planipennis
The Emerald Ash Borer is an insect native to Asia, specifically Korea, Japan, northern China, and eastern Russia. First detected in North America in Michigan in 2002, it is thought to have been introduced in the 1990s in wood used to crate products. Native ash trees have little or no resistance to this insect. It has infested over twenty-one million ash trees. The insect kills the tree when the larvae burrow into it by eating the cambium layer, girdling the trunk. The tree can no longer transport nutrients and dies.

The Emerald Ash Borer can fly approximately one-half mile (0.8 km) from the trees from which they emerge. However, it is spreading faster than it can be contained. People transporting firewood accelerate a problem that could cost billions of dollars nationwide. To help curb the spread of the Emerald Ash Borer, purchase firewood at or near your campsite and leave remaining firewood behind.
Sirex Wood Wasp
David R. Lance, USDA APHIS PPQ

Sirex Woodwasp

Sirex noctilio
Sirex Woodwasp is native to Europe, Asia, and northern Africa. It was first detected in the wild in North America in 2004 in Fulton, New York. It causes significant mortality to many valuable species of pine. It is attracted to pine trees under stress. This stress can come from drought, fire, or other debilitating conditions.

Pines are often used to make solid-wood packing material, telephone poles, and furniture. Since the insect’s life cycle can take one year or more to complete, Sirex Woodwasp is often transported in pallets or other types of solid-wood packing material.

This invader has been detected in New York, Pennsylvania, Michigan, and Vermont, and it is well established in Ontario, Canada.

Chinese Mitten Crab

Eriocheir sinensis
The Chinese Mitten Crab is native to eastern Asia. It is named for the fine and dense setae (hairs) present on its claws. First collected in North America in Ontario in 1965, it was discovered in the Hudson River in 2007. The Chinese Mitten Crab was probably introduced multiple times into North America in ship ballast water or as live releases from crabs purchased as food.

The Chinese Mitten Crab can be particularly destructive in new habitats. Its burrowing ability can seriously erode the banks of rivers and levees. Large populations can displace native crabs and crayfish. This catadromous crab moves into freshwater and spends most of its life in streams but spawns in salt water. It has been reported several hundred kilometers inland in some drainages, often traveling on land to bypass barriers.
Asian Shore Crab
U.S. Geological Survey

Asian Shore Crab

Hemigrapsis sanguineus
The Asian Shore Crab is native to the western Pacific Ocean. It is easily distinguishable with its square carapace, banded legs, and red spots on each claw. Although small in size, females can release 150,000 to 200,000 larvae each year. First reported in the Northeast in 1988, it has since been found from Maine to North Carolina.

Asian Shore Crab was probably initially introduced in ballast water. It has the potential to compete with or prey upon native species. Recent trends show the number of native crabs decreasing in areas where Asian Shore Crab populations have been increasing.
Golden Nematode These roots show many of the roundworm cysts, some golden in color. These are the mature nematodes, and their color gives the species its common name. (Cornell University)

Golden Nematode affects crop
This photograph from 1960 shows damage the Golden Nematode caused to a potato crop on Long Island.

Golden Nematode

Globodera rostochiensis
Golden Nematode is native to South America and was discovered in the United States in 1941. It was responsible for damaging a potato field on Long Island. Golden Nematodes do not easily disperse without help. They spread into new areas as cysts on seed potatoes, nursery stock, and in contaminated soil. It has been confined to nine counties within New York state. This is due to an effective, fifty-year-old, quarantine.

The best method of control is crop rotation using potato varieties resistant to Golden Nematode and non-host crops. This approach is preferable to chemical treatments that are expensive, can cause environmental damage, and cannot guarantee eradication. Infestation of new areas results in severe economic effects due to quarantine restrictions placed on agricultural products in affected areas.
Norway Rat
Dr. Antonio J. Ferreira © California Academy of Sciences

Norway Rat

Rattus norvegicus
The Norway Rat, native to China, was introduced in the United States around 1776. Now globally widespread, it has been moved on ships as stowaways or in cargo.

Its effect is largely restricted to cities and farms, where it eats and contaminates stored food and grains. It also transmits numerous diseases, such as Hantavirus and typhus. On islands around the world, Norway Rats are major predators of many native species that have evolved in a predator-reduced environment.
Red Shrimp
S. Pothoven, NOAA, Great Lakes Environmental Research Laboratory

Bloody Red Shrimp

Hemimysis anomala
It is a freshwater, shrimp-like crustacean, 1/4- to 1/2- inch (6 to 13 mm) long and is native to eastern Europe and western Asia. It is believed to have been introduced into the Great Lakes in the freshwater ballast of international ships. The Bloody Red Shrimp was first discovered in May 2006 at Nine Mile Point in southeastern Lake Ontario. Since that time, this crustacean has also been found elsewhere in Lake Ontario and in Lake Erie.

Bloody Red Shrimp rest on the lake bottom during the day. By night, they migrate to forage in swarms in the upper levels of the water column. The potential exists for this crustacean to cause substantial ecological harm. It could reduce the biomass and diversity of infested waters.