Presented by Garrett Noles

Hydrilla verticillata (L.f.) Royle

Common Names + Synonyms

• Common- Hydrilla, water thyme, Florida elodea

• Latin binomials- Hottonia serrata, Hydrilla angustifolia, Hydrilla ovalifolia, Leptanthes verticillata, Serpicula verticillata, Elodea verticillata

www.cal-ipc.org

Photo by USDA/ARS

Taxonomy

• Family- Hydrocharitaceae (Tape-grass family)• Reproduction- Mainly vegetative propagationDioecious (mostly in US) & rarely monoecious• Morphology- Stems: long and slender, white in color Leaves- dark green, strap shaped, saw-toothed margins Grow in dense clusters, branching towards surface of water

www.cal-ipc.org

Turions

• Turions- “dark green buds on some leaf axils”

• Subterranean turions- yellow tuber like buds attached to root folicles

plants.ifas.ufl.edu

Current distribution of Hydrilla verticillata

USDA Plants 2010

Ecological Impacts

• Can outcompete other desirable aquatic plants • Can slow water flow thus increase water

temperature• Can use the oxygen resources in a water body • Some evidence of allelopathy discouraging plant

biodiversity (if interested view starred paper) • Can alter important freshwater fish habitat

Economic Impacts

• Can reduce water recreation • Turions and fragments can clog irrigation

canals• Can reduce hydropower productivity • Mechanical and chemical treatments can add

up over a period of time to be costly

Biological Control

• Hydrilla leaf-mining fly and hydrilla tuber weevil

• Both found in India mid 80’s

• Are major species specific predators for Hydrilla

plants.ifas.ufl.edu

Insect Herbivory Effects

• 14,000 L tanks • Each divided into 32

sections • Competition tests and

herbivory tests in different tanks

• Concluded that combo of bio controls are most effective

Doyle et.al. 2007

Bio Control Cont.

• Another biological enemy to hydrilla from Asia

• Grow fast, and consume tubers/turions!

• However, grass carp are not species specific foragers

Ctenopharyngodon idella (Grass Carp)

www.ecy.wa.gov

Effectiveness of Grass Carp

• Consume large amounts until they reach maximum size

• Smaller fish consume more vegetation

• Once size limit is reached, no longer a great control agent

Osborne 1981

Chemical Controls

• Endothall (Aquathol K)Can be used selectively Kills vegetation, not

tubers• Diquat (Reward) Is effected by water

solids(silt) Usually used for one

season

• Reward prices vary, check local provider ($130-150/gallon)

• Aquathol powder form prices also vary ( $240-260/10 lbs)

• Aquathol liquid form ($240-260/ 2.5 gallons)

www.ecy.wa.gov

Work Cited • California Invasive Plant Council (2010) Cal-IPC Resources on Hydrilla verticillata. http://www.cal-

ipc.org/ip/management/plant_profiles/Hydrilla_verticillata.php, April 18, 2010.

• Doyle R, Grodowitz M, Smart M, Owens C (2007) Separate and interactive effects of competition and herbivory on the growth, expansion, and tuber formation of Hydrilla verticillata. Biological Control 41: 327-338.

• Kulshreshtha M, Gopal B (1983) Allelopathic influence of Hydrilla verticillata on the distribution of Ceratophyllum species. Aquatic Botany 16: 207-209. *

• Osborne JA, Sassic NM (1981) The size of grass carp as a factor in the control of Hydrilla. Aquatic Botany 11: 129-136.

• University of Florida IFAS (2009) Center for Aquatic and Invasive Plants.http://plants.ifas.ufl.edu/node/183, April 17, 2010

• USDA, ARS. 2010. The Agriculture Research Service Database (http://www.ars.usda.gov, 21 April 2010). ARS Headquarters, Washington DC, 20250.

Work Cited Cont.• USDA, NRCS. 2010. The PLANTS Database (http://plants.usda.gov, 21 April 2010).

National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

• Washington State Department of Ecology (2010) Aquatic Plant Management- Aquatic Herbicides. http://www.ecy.wa.gov/programs/wq/plants/management/aqua028.html, April 16, 2010.

• Washington State Department of Ecology (2010) Aquatic Plant Management- Triploid Grass Carp. http://www.ecy.wa.gov/programs/wq/plants/management/aqua024.html, April 17, 2010.