MISSISSIPPI'S TEN WORST INVASIVE WEEDS:
THREATENING FISH AND WILDLIFE HABITAT
BY FAYE WINTERS, JOHN D. BYRD, JR., AND CHARLES T. BRYSON

Mississippi is being silently invaded by exotic plant species. These exotic weeds are not just nuisances in urban and agricultural areas; they are changing the way natural areas function and they are costing all of us money. Your tax dollars help pay to fight the disruptive spread of these plants. Also, revenues are lost when plants such as kudzu and cogongrass invade forestlands.
This invasion has gained momentum since the last century when many of these plants were first imported or accidentally introduced. It is estimated that invasive exotic plants already affect 100 million acres in the United States and that the cost of all exotics, plants, animals and pathogens in the United States may exceed $4 billion annually. This acreage increases annually by an area twice the size of Delaware. Almost 20 percent of the plant species in Mississippi’s forests, parks, refuges and other open spaces are not native to our state while as many as 70% of the weeds in agricultural areas are not native. Most of these exotic plants meet few natural constraints and can soon dominate a landscape.
The “10 worst weeds” described in this article are biological pollutants that crowd out native plants, degrade fish and wildlife habitat and contribute to the further decline of at-risk, threatened and endangered species. Many of these plants are familiar sights on our landscape. All of them threaten the biological diversity of Mississippi.


ALLIGATORWEED
(ALTERNANTHERA PHILOXEROIDES)
Photo by Mississippi Fish and Wildlife Foundation.


Native to South America. Appeared in the United States about 1890.

Alligatorweed is a serious pest in Mississippi where it occupies large areas of wetlands that would otherwise be available to native wetland plants. It can grow in dry fields or in water. It generally grows as a mat of interwoven plants that often cover the entire surface of a waterway. A South American leaf beetle was introduced in the 1980s for biological control of alligatorweed. This beetle has reduced the spread of this plant but has not eliminated it or completely eliminated the spread into areas previously not infested by alligatorweed.

JAPANESE HONEYSUCKLE
(LONICERA JAPONICA)
Photo by Charles Bryson.


Native to Japan. First introduced to Long Island, New York, in 1862.

Japanese honeysuckle is a familiar plant in the southern landscape where it provides year round forage for deer and other wildlife. It is common along fence rows, forest openings and disturbed areas. However, this plant's dense growth crowds out native vegetation, reduces the variety of native plants available to wildlife and can stunt or kill growing trees. Note: Coral honeysuckle, Cross Vine and Virginia creeper are useful native vines for home landscaping instead of exotic Japanese honeysuckle.

CHINESE PRIVET
(LIGUDSTRUM SINENSE)
Photo by John Byrd.


Native to China. Introduced in the United States as an ornamental shrub in 1852.

Found throughout the South, Chinese privet forms dense thickets along roadsides, fence rows, fields, rights of way and in forested creek bottoms. These shrubs typically reach 10 to 20 feet in height with numerous branches. A member of the olive family, privet produces seeds abundantly and regenerates by root sprouts quickly forming dense stands. Because of dense stand production, privet crowds out native plants and trees, especially hardwoods. Privet typically produces small white flowers in spring or early summer and terminal clusters of fruit in the fall. Fruit and seeds are consumed primarily by birds and disseminated.

CHINESE TALLOW TREE (POPCORN TREE)
(TRIADICA SEBIFERA)
Photo by Charles Bryson.


Native to Eastern Asia. Imported to South Carolina in the late 1700s and later used in soap making and for firewood where growth of other hardwood trees was too slow for the demand.

The colorful fall foliage, popcorn-like fruit and rapid growth of Chinese tallow make it a popular landscape tree. It reproduces easily, spreads quickly, and is difficult to control because of its long taproot. By displacing native vegetation under bottomland hardwood forests, Chinese tallow has become a serious pest in south Mississippi in recent years. Several states are in the process of banning sales of Chinese tallow after widespread invasions of wetlands from Texas to Florida.

COGONGRASS
(IMPERATA CYLINDRICA)
Photo by U.S. Fish and Wildlife Service.


Native to Southeast Asia. Arrived accidentally as packing material into Mobile Bay, Alabama, in the early 1900s. Used by the Soil Conservation Service for erosion control. It was later promoted as a forage grass and as an ornamental.

Classified as the seventh worst weed in the world, cogongrass is hardy and tolerant of shade, high salinity and drought. It forms dense mats that crowd out native vegetation and forage plants and displaces ground nesting species, such as turkey and bobwhite quail. It can alter the natural fire regime by causing hotter and more frequent fires. Note: Cogongrass is still sold as an ornamental under the name of Japanese bloodgrass or "Red Baron" bloodgrass. Note: Many native grasses are non-invasive and more spectacular for the home landscape than cogongrass cultivars.


JOHNSONGRASS
(SORGHUM HALEPENSE)
Photo by John Byrd.


Native to the Mediterranean region. Came to the United States as a forage plant in early 1800s.

Johnsongrass has spread throughout most of the temperate area of the world. Growing up to 8 feet tall and forming almost pure stands, Johnsongrass is a serious weed of row crops, pastures and roadside rights of way throughout Mississippi. Spreading by prolific seed production or fleshy, underground rhizomes, Johnsongrass stands along highway rights of way can provide hiding sites for wildlife or limit visibility of passing motorists. Rank growth or growth that occurs under adverse growing conditions for Johnsongrass can cause cyanide poisoning in animals, and can be especially dangerous to ruminants.



KUDZU
(PUERARIA LOBATA)
Photo by Mississippi Fish and Wildlife Foundation.


Native to Japan and Asia. Showcased as an ornamental at the Philadelphia Centennial Exposition in 1876. In Mississippi, it was planted to control widespread soil erosion that plagued the state in the last half of the 19th century and the first half of the 20th century.

No list of Mississippi weeds would be complete without the "Plant that Ate the South." During summers, kudzu grows up to a foot a day, covering trees, buildings, fences and telephone poles. Kudzu damages structures and eventually kills trees and understory growth. This vine has caused more than $100 million in damages.



TROPICAL SODA APPLE
(SOLANUM VIARUM)
Photo by Charles Bryson.


Native to Brazil and Argentina. First recorded in Glades County, Florida in 1988.

Within 10 years of its arrival, tropical soda apple invaded an estimated 1.5 million acres in five southern states and Puerto Rico. It spreads by interstate movement of cattle, hay and composted manure from infested areas. This prickly plant replaces edible forage plants and hampers livestock and wildlife movement. It is a serious threat for vegetable growers, livestock producers and land managers.



PURPLE LOOSESTRIFE
(LYTHRUM SALICARIA)
Photo by John Byrd.


Native to Eurasia. Introduced for ornamental and medicinal uses in 1800s.

This troublesome species is just reaching Mississippi following a widespread invasion of the northern plain states. A deceptively beautiful flowering plant, purple loosestrife can completely take over wetlands where it crowds out native plants and negatively impacts native fish and wildlife. Purple loosestrife covers about 4 million wetland acres nationally and costs about $45 million a year in control efforts. Early detection and aggressive local control will be the key to keeping this plant from spreading in Mississippi. Note: Research has shown that "sterile" varieties sold in nurseries can still reproduce and become invasive.



WATER HYACINTH
(EICHORNIA CRASSIPES)
Photo by Michael Kelly.


Native to the Amazon Basin and South America. Imported into the United States as an aquatic ornamental in 1884.

Water hyacinth may be the world's worst aquatic weed. Sold as a water garden ornamental famous for its beautiful flowers, it has escaped into wetlands and waterways across the globe. One of the fastest growing plants known, it displaces native plants, fish and wildlife, disrupts water transportation, disturbs recreational fishing and blocks water intakes at hydroelectric power generating dams. At one time in Florida, 125,000 acres of open water were covered with up to 200 tons of water hyacinth per acre.


YOU CAN HELP STOP THE INVASION!

• Refrain from planting Mississippi's “ten worst weeds.” Appealing as some may be, these plants are all notorious for escaping and invading outlying areas.
• Use nursery raised native plants. Ask your local nursery staff for suggestions or check out native gardening books from your local library or bookstore.
• Remove these plants from your property. If needed, contact your county Extension agent for recommended methods of chemical control. Use herbicides carefully. Many herbicides are not selective and will kill all surrounding vegetation or may harm aquatic systems.
• Contact your local USDA Service Center to see if any of these invasive species are eligible for cost-share assistance through such conservation programs as the Environmental Quality Incentives Program.
• Help control exotic plants on nearby public lands. This can be an educational and productive activity for scouts, 4 H clubs and other service groups. Check with your local highway department, forest, refuge or park for exotic plant removal projects.

This article was written by Faye Winters, Field Wildlife Biologist, Bureau of Land Management in Jackson, John D. Byrd, Jr., PhD, Extension Weed Specialist with Mississippi State University in Starkville, and Charles T. Bryson, PhD, Research Botanist with the U.S. Department of Agriculture's Agriculture Research Service in Stoneville.