Aquatic Plant Control Research Program (APCRP) Publications
The U.S. Army Engineer Research and Development Center announces the publication
of a new document on its Web site. Visit our Aquatic Plant Control Research
Program Web site http://el.erdc.usace.army.mil/programs.cfm?Topic=apcrp.

ERDC/EL SR-05-1
A Survey of the Invasive Aquatic and Riparian Plants of the Lower Rio Grande,
2004
by Chetta S. Owens, Michael J. Grodowitz, and Fred Nibling

Abstract:
Hydrilla has exhibited extensive range expansion along the Rio Grande since it
was first discovered in early 1990 and is now found in areas far removed from
the original infestation in Brownsville, TX. Hydrilla, a nonindigenous aquatic
plant species, has been implicated in restricted water delivery, inaccurate
water accounting, and an overall breakdown of system maintenance. The presence
of hydrilla also has had a decided impact on native flora by the formation of
extensive monocultures in many areas.
In 2004, surveys were conducted starting below Amistad Reservoir to immediately
below Falcon Reservoir to assess the distribution and expansion of hydrilla
infestations and document the presence of other invasive aquatic and riparian
plant species. A total of seven nonindigenous plant species, hydrilla (Hydrilla
verticillata), Eurasian watermilfoil (Myriophyllum spicatum), parrotfeather (M.
aquaticum), elephant-ear (Colcasia esculenta), giant cane (Arundo donax), salt
cedar (Tamarisk spp.), and castorbean (Ricinus communis) were observed. Hydrilla
infestations that were originally discovered during 2003 had increased in size
through localized stolon expansion. Also, new hydrilla sites were discovered in
2004, including several directly below Amistad Reservoir. No hydrilla was
discovered immediately south of Laredo; however, hydrilla infestations had
dramatically increased below Falcon Reservoir. Giant cane continues to spread
down river, even displacing well-established common cane (Phragmites australis)
below Falcon Reservoir. While no new Eurasian watermilfoil sites were discovered
in 2004, existing infestations near Del Rio remain stable, extending
bank-to-bank and considerable distances down the river. Eurasian watermilfoil
fragments, which could lead to the formation of new infestations downstream,
were observed in the river. Numerous new sites of parrotfeather, elephant-ear,
and salt cedar were found during the 2004 survey, and all sites identified in
2003 had increased in localized spread. One endangered wetland plant species,
Correll's false dragonhead (Physostegia correllii), was tentatively identified.

If you wish to access/download the document (26 pages, 1.1 MB) in pdf format,
the address is: http://libweb.wes.army.mil/uhtbin/hyperion/EL-SR-05-1.pdf

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