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Alligatorweed Biology Ecology and Management
1. 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
2. Benefits of Aquatic Plants
Stabilize 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
3. Non-native vs. Native Community
Myriophyllum spicatum Vallisneria americana
Eurasian watermilfoil Water celery
7. 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)
10. Alligatorweed Habitat
Nuisance in subtropical
aquatic and wetland areas,
can be rooted in submersed
to moist soil, especially ditch
and stream habitats, forms
floating mats
Major problem in the Ross
Barnett Reservoir and MS
Delta
Potentially has two biotypes Ross Barnett Reservoir, MS
11. Alligatorweed ID
Non-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)
12. 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
14. Can Be Confused With:
Sessile joyweed (Alternanthera sessilis)
Not widespread
Ludwigia spp.
StarrImages
Kim Starr
15. Ecological Impacts
Degradation of water quality
Reduction in species diversity
Suppresses native plant species
Potential impacts on endangered
species
Alters animal communities
16. Lake Jackson, MS Blue Lake, MS
Little Eagle Lake, MS Blue Lake, MS
17. Human Use Impacts
Reduces access to water
Reduces property values
Limits recreation
Impedes navigation
Increases flood duration
& intensity
Lake Jackson, MS
Human health Alligatorweed
20. Biological Control
Alligatorweed flea beetle
(Agasicles hygrophila)
Works well south of
Vicksburg-Jackson-
Montgomery (I-20
corridor)
21. Biological Control
Stem borer moth (Vogtia malloi)
Active throughout MS
May be more of an option for
Missouri than flea beetle due to (Photograph courtesy USDA, ARS by Willey C. Durden.)
climate
Typically not present near
agricultural areas where
insecticides are used
(Photograph courtesy USDA, ARS)
22. Small Scale Trials
Imazapyr, 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
23. Field Control
Imazapyr, 1 to 4 pints/acre
Triclopyr, 3 to 8 quarts/acre
2,4-D, 2 quarts/acre
Glyphosate, 2 quarts/acre
Non-ionic surfactant, 1 pint/acre
In Mississippi, 2,4-D and glyphosate are being used
alone or as a tank mix
Always read the herbicide label
25. Other Resources
UNIVERSITY PROFESSIONAL SOCIETY
Center for Aquatic and Invasive Plants Aquatic Plant Management Society
aquat1.ifas.ufl.edu www.apms.org
Mississippi State University GRI North American Lake Management Society
www.gri.msstate.edu www.nalms.org
MSU Extension Service GOVERNMENT
msucares.com/pubs/publications/p1532aquat Aquatic Plant Control Research Program
ic.pdf www.wes.army.mil/el/aqua/aqua.html
USGS Aquatic Nonindigenous Species Site
FOUNDATION nas.er.usgs.gov
Aquatic Ecosystem Restoration Foundation
www.aquatics.org
26. 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