Texas Invasives

Sign up for the iWire to get breaking news, event info and the species spotlight.

Return to List | Printer Friendly Version

Hydrilla verticillata - Hydrilla

View record in Invasive Plant database.
Download Assessment: PDF.

SUMMARY

Rating	Alert	Impact	Invasiveness	Distribution	Doc.
High	N	A	A	A	3.38
Comments:
Rating 1 = High 2 = Moderate 3 = Limited 4 = Evaluated, not listed		Alert Y = Yes N = No	Scores A = Severe B = Moderate C = Limited D = None U = Unknown	Documentation 4 = Reviewed scientific publications 3 = Other published material 2 = Observational 1 = Anecdotal 0 = No information

Scores

1.1	1.2	1.3	1.4	2.1	2.2	2.3	2.4	2.5	2.6	2.7	3.1	3.2
A	A	A	D	A	A	B	A	A	A	A	A	A

IMPACT

1.1 Impact on abiotic ecosystem processes - A

Identify ecosystem processes impacted: Dense underwater stands of hydrilla raise water pH and temperature, and lower dissolved oxygen.

Sources of information: Hydrilla. Technical Information about Hydrilla. 1999. Accessed: 06 July 11: http://www.ecy.wa.gov/programs/wq/plants/weeds/hydrilla.html. Langeland, K.A. 1996. Hydrilla verticillata (L.F.) Royle (Hydrocharitaceae), "The Perfect Aquatic Weed." Castanea 61:293-304. The Quiet Invasion: A Guide to Invasive Plants of the Galveston Bay Area. Lisa Gonzalez and Jeff DallaRosa. Houston Advanced Research Center, 2006.

Documentation: Rev'd Sci. Pub'n

1.2 Impact on plant community composition, structure, and interactions - A

Identify type of impact or alteration: It will grow with less light and is more efficient at taking up nutrients than native species.

Taken from California Invasive Plant and Pest Council:

Physical blockage displaces native aquatic vegetation by forming dense stands or large subsurface mats. Dense canopies can often shade out native vegetation. Hydrilla can grow at lower light intensities than many other plants, absorb carbon from water more efficiently than other plants and can continue to thrive during the summer when carbon can become limiting, store extra P, tolerant of a wide range of water conditions, will thrive in flowing and still water, and tolerate salinity of up to 10 ppt, encroaching upon outer limits of estuaries.

Sources of information: Hydrilla. Technical Information about Hydrilla. 1999. Accessed: 06 July 11: http://www.ecy.wa.gov/programs/wq/plants/weeds/hydrilla.html.

Langeland, K.A. 1996. Hydrilla verticillata (L.F.) Royle (Hydrocharitaceae), "The Perfect Aquatic Weed." Castanea 61:293-304.

The Quiet Invasion: A Guide to Invasive Plants of the Galveston Bay Area. Lisa Gonzalez and Jeff DallaRosa. Houston Advanced Research Center, 2006.

Documentation: Rev'd Sci. Pub'n

1.3 Impact on higher trophic levels - A

Identify type of impact or alteration: While the opinion that hydrilla is beneficial for sportfish production is supported by certain research, other research suggests that largemouth bass are adversely affected when Hydrilla coverage exceeds 30%. While the number of fish is often increased, large fish become rarer.

Sources of information: Langeland, K.A. 1996. Hydrilla verticillata (L.F.) Royle (Hydrocharitaceae), "The Perfect Aquatic Weed." Castanea 61:293-304.

The Quiet Invasion: A Guide to Invasive Plants of the Galveston Bay Area. Lisa Gonzalez and Jeff DallaRosa. Houston Advanced Research Center, 2006.

Documentation: Rev'd Sci. Pub'n

1.4 Impact on genetic integrity - D

Identify impacts: No known hybridization. No native Hydrilla species

Sources of information: Waitt, D. 2011. Native Plant Information Network. Accessed 6 July 2011: http://wildflower.org/plants/

Documentation: Other Pub. Matl

IMPACT: A A A D = A

INVASIVENESS

2.1 Role of anthropogenic and natural disturbance in establishment - A

Describe role of disturbance: No disturbance needed. Was introduced through aquarium trade and can be passed easily between water bodies on boats and trailers.

Sources of information: Hydrilla. Technical Information about Hydrilla. 1999. Accessed: 06 July 11: http://www.ecy.wa.gov/programs/wq/plants/weeds/hydrilla.html.

Documentation: Other Pub. Matl

2.2 Local rate of spread with no management - A

Describe rate of spread: Hydrilla was first discovered in Lake Austin in July 1999, when Texas Parks and Wildlife (TPWD) documented approximately 23 acres of the plants. By July 2000, growth had increased to 200 acres.

Sources of information: Gilroy, M. 2011. Hydrilla. City of Austin Watershed Protection Department. Accessed 6 July 2011: http://www.ci.austin.tx.us/watershed/hydrilla_faqs.htm#done.

Documentation: Other Pub. Matl

2.3 Recent trend in total area infested within state - B

Describe trend: Hydrilla is actively controlled in reservoirs and usually in publicly owned bodies of water therefore is not doubling in size every ten years. But without management Hydrilla could quickly spread into water bodies were it is not present.

Sources of information: Gilroy, M. 2011. Hydrilla. City of Austin Watershed Protection Department. Accessed 6 July 2011: http://www.ci.austin.tx.us/watershed/hydrilla_faqs.htm#done.

Documentation: Other Pub. Matl

2.4 Innate reproductive potential - A

Describe key reproductive characteristics: Refer to Worksheet A.

Sources of information: Hydrilla. Technical Information about Hydrilla. 1999. Accessed: 06 July 11: http://www.ecy.wa.gov/programs/wq/plants/weeds/hydrilla.html. >br>
Langeland, K.A. 1996. Hydrilla verticillata (L.F.) Royle (Hydrocharitaceae), "The Perfect Aquatic Weed." Castanea 61:293-304.

The Quiet Invasion: A Guide to Invasive Plants of the Galveston Bay Area. Lisa Gonzalez and Jeff DallaRosa. Houston Advanced Research Center, 2006.

Documentation: Rev'd Sci. Pub'n

2.5 Potential for human-caused dispersal - A

Identify dispersal mechanisms: Hydrilla is easily and commonly spread by fragments on boats and boat trailers

Sources of information: Gilroy, M. 2011. Hydrilla. City of Austin Watershed Protection Department. Accessed 6 July 2011: http://www.ci.austin.tx.us/watershed/hydrilla_faqs.htm#done.

Hydrilla. Technical Information about Hydrilla. 1999. Accessed: 06 July 11: http://www.ecy.wa.gov/programs/wq/plants/weeds/hydrilla.html.

Langeland, K.A. 1996. Hydrilla verticillata (L.F.) Royle (Hydrocharitaceae), "The Perfect Aquatic Weed." Castanea 61:293-304.

The Quiet Invasion: A Guide to Invasive Plants of the Galveston Bay Area. Lisa Gonzalez and Jeff DallaRosa. Houston Advanced Research Center, 2006.

Documentation: Rev'd Sci. Pub'n

2.6 Potential for natural long-distance dispersal - A

Identify dispersal mechanisms: Hydrilla can grow by fragmentation or tubers that can both be broken off and carried long distances down waterways. Tubers can survive ingestion by water fowl. There is potential for seeds to be spread by waterfowl and other birds.

Documentation: Rev'd Sci. Pub'n

2.7 Other regions invaded - A

Identify other regions: Hydrilla has the potential to grow in any waterway in Texas and has not invaded all of them. Therefore it is a great threat to waterways where it is not currently present.

Sources of information: Observation: T. Gallo

Documentation: Observational

INVASIVENESS: A A B A A A A = A

DISTRIBUTION

3.1 Ecological amplitude - A

Describe ecological amplitude, identifying date of source information and approximate date of introduction to the state, if known: Refer to Worksheet B. Hydrilla is severely underreported in Texas.

Sources of information: Invaders of Texas Citizen Science Observations (Accessed 8 July 2011: http://texasinvasives.org/observations/search.php?satellite=&sn=HYVE3&cn=

USDA PLANTS Database (Accessed 8 July 2011: http://plants.usda.gov/java/county?state_name=Texas&statefips=48&symbol= HYVE3)

Documentation: Other Pub. Matl

3.2 Distribution/Peak frequency - A

Identify type of impact or alteration: Refer to Worksheet B. Hydrilla is severely underreported in Texas.

Documentation: Other Pub. Matl

IMPACT: A A = A

TEXAS ECOREGIONS

Source: Level III and IV Ecoregions of Texas. Griffith, G.E., Bryce, S.A., Omernik, J.M., Comstock, J.A., Rogers, A.C., Harrison, B., Hatch, S.L., and Bezanson, D., 2004, Ecoregions of Texas, U.S. Environmental Protection Agency, Corvallis, OR.

Score: A. means >50% of type occurrences are invaded; B means >20% to 50%; C. means >5% to 20%; D. means present but ≤5%; U. means unknown.

Code	Level III	Level IV	Score
ER01	Arizona/New Mexico Mountains	Chihuahuan Desert Slopes	U
ER01	Arizona/New Mexico Mountains	Montane Woodlands
ER02	Chihuahuan Deserts	Chihuahuan Basins and Playas
		Chihuahuan Desert Grasslands
		Low Mountains and Bajadas
		Chihuahuan Montane Woodlands
		Stockton Plateau
ER03	High Plains	Rolling Sand Plains
		Canadian/Cimarron High Plains
		Llano Estacado
		Shinnery Sands
		Arid Llano Estacado
ER04	Southwestern Tablelands	Canadian/Cimarron Breaks
		Flat Tablelands and Valleys
		Caprock Canyons, Badlands, and Breaks
		Semiarid Canadian Breaks
ER05	Central Great Plains	Red Prairie
		Broken Red Plains
		Limestone Plains
ER06	Cross Timbers	Eastern Crosstimbers	A
		Western Crosstimbers
		Grand Prairie
		Limestone Cut Plain
		Carbonate Cross Timbers
ER07	Edwards Plateau	Edwards Plateau Woodland
		Llano Uplift
		Balcones Canyonlands	A
		Semiarid Edwards Plateau
ER08	Southern Texas Plains	Northern Nueces Alluvial Plains
		Semiarid Edwards Bajadas
		Texas-Tamaulipan Thornscrub
		Rio Grande Floodplain and Terraces
ER09	Texas Blackland Prairies	Northern Blackland Prairies
		Southern Blackland/Fayette Prairie
		Floodplains and Low Terraces
ER10	East Central Texas Plains	Northern Post Oak Savanna
		Southern Post Oak Savanna	A
		San Antonio Prairie
		Northern Prairie Outliers
		Bastrop Lost Pines
		Floodplains and Low Terraces
ER11	Western Gulf Coastal Plain	Northern Humid Gulf Coastal Prairies
		Southern Subhumid Gulf Coastal Prairies
		Floodplains and Low Terraces
		Coastal Sand Plain
		Lower Rio Grande Valley
		Lower Rio Grande Alluvial Floodplain
		Texas-Louisiana Coastal Marshes
		Mid-Coast Barrier Islands and Coastal Marshes
		Laguna Madre Barrier Islands and Coastal Marshes
ER12	South Central Plains	Tertiary Uplands
		Floodplains and Low Terraces
		Pleistocene Fluvial Terraces
		Southern Tertiary Uplands
		Flatwoods
		Red River Bottomland

EVALUATORS

Evaluation Date: 2011-07-06

Evaluator 1
Travis Gallo/Ecologist
The Lady Bird Johnson Wildflower Center
512-232-0116
tgallo@wildflower.org
4801 La Crosse Ave., Austin, Texas 78704

Evaluator 2

REVIEW

Reviewers:
Review Date: 0000-00-00
Comments:

REFERENCES

Originally assessed for the City of Austin Invasive Management Plan

TexasInvasives.org - Home

Invasives Database

Sign up for the iWire to get breaking news, event info and the species spotlight.

Hydrilla verticillata - Hydrilla

SUMMARY