Ryan M. Wersal, Ph.D.Mississippi State University

Geosystems Research Institute

Missouri Department of Conservation Invasive Plant Workshop

Powder Valley Nature Center, Kirkwood, MO May 16th and 17th

Benefits of Aquatic PlantsStabilize lake sediments,

reduce resuspension

Increase sedimentation, reduce turbidity

Provide habitat for insects, forage fish, fish spawning and YOY fish

Provide food for waterfowl, other animals

Non-native vs. Native Community

Myriophyllum spicatumEurasian watermilfoil

Vallisneria americanaWater celery

Canopy Structure

Alligatorweed(Alternanthera philoxeroides)

Emergent perennial native to South America (Vogt et al. 1979)

Nuisance aquatic species in over 32 countries worldwide (Gunasekera and Bonila 2001)

Major problem in Southern U.S. aquatic and riparian areas (Kay and Haller 1982)

Hollow stems form extensive, dense mats on water surface (Kay and Haller 1982)

Impedes boat traffic, increases flood risk, clogs irrigation canals, harbors pathogen-carrying insects, reduces overall water quality and property value (Madsen 2004)

Alligatorweed distribution in the United States by Hydrologic Units

Alligatorweed distribution in the MidSouth Region

Alligatorweed HabitatNuisance in subtropical

aquatic and wetland areas, can be rooted in submersed to moist soil, especially ditch and stream habitats, forms floating matsMajor problem in the

Ross Barnett Reservoir and MS Delta

Potentially has two biotypes

Ross Barnett Reservoir, MS

Alligatorweed IDNon-native emergent

perennial plant

Emergent or submersed

Stems form a tangled mass

Leaves simple and opposite on stems

Leaves elliptical

Typically glabrous (very little if any hair)

Alligatorweed ID

Several-flowered whitish head

Flowers borne in leaf axils

Flowers always on stalks up to 2 inches in length

Mature seeds not known to occur

Spread via vegetative growth and fragmentation

Alligatorweed IDKey identifying characteristic:

Stems almost always hollow

Can Be Confused With:Sessile joyweed (Alternanthera sessilis)

Not widespread

Ludwigia spp.StarrImages

Kim Starr

Ecological ImpactsDegradation of water quality

Reduction in species diversity

Suppresses native plant species

Potential impacts on endangered species

Alters animal communities

Lake Jackson, MS Blue Lake, MS

Little Eagle Lake, MS Blue Lake, MS

Lake Jackson, MSAlligatorweed

Human Use ImpactsReduces access to

water

Reduces property values

Limits recreation

Impedes navigation

Increases flood duration & intensity

Human health

Management Options

Biological

Chemical

Mechanical

Physical

Institutional

Alligatorweed ManagementBiological

Alligatorweed flea beetleStem borer moth

Chemical2,4-D, triclopyr, imazapyr, glyphosate

Mechanical - None

Physical - None

Biological ControlAlligatorweed flea

beetle (Agasicles hygrophila)

Works well south of Vicksburg-Jackson-Montgomery (I-20 corridor)

Biological ControlStem borer moth (Vogtia

malloi)

Active throughout MS

May be more of an option for Missouri than flea beetle due to climate

Typically not present near agricultural areas where insecticides are used

(Photograph courtesy USDA, ARS by Willey C. Durden.)

(Photograph courtesy USDA, ARS)

Small Scale TrialsImazapyr, triclopyr, glyphosate (DIA salt and IPA

salt), imazamox, 2,4-D, diquat (maximum label rate), and penoxsulam (maximum label rate) offered similar effective control for 12 weeks

Carfentrazone and diquat provided rapid biomass reduction but regrowth began within days after application

Field ControlImazapyr, 1 to 4 pints/acreTriclopyr, 3 to 8 quarts/acre2,4-D, 2 quarts/acreGlyphosate, 2 quarts/acreNon-ionic surfactant, 1 pint/acreIn Mississippi, 2,4-D and glyphosate are

being used alone or as a tank mix

Always read the herbicide label

Hobbs and Humphries 1995. Conserv. Biol. 9:761-770.

Other ResourcesUNIVERSITYCenter for Aquatic and Invasive Plants

aquat1.ifas.ufl.eduMississippi State University GRI

www.gri.msstate.eduMSU Extension Service

msucares.com/pubs/publications/p1532aquatic.pdf

FOUNDATIONAquatic Ecosystem Restoration Foundation

www.aquatics.org

PROFESSIONAL SOCIETYAquatic Plant Management Society

www.apms.org North American Lake Management Society

www.nalms.org

GOVERNMENTAquatic Plant Control Research Program

www.wes.army.mil/el/aqua/aqua.htmlUSGS Aquatic Nonindigenous Species Site

nas.er.usgs.gov

Ryan Wersal, Ph.D.

Geosystems Research Institute

Box 9652

Mississippi State, MS 39762

Ph (662) 325-4595

Fax (662) 325-7692

rwersal@gri.msstate.edu