Hydrilla Invades Washington, D.C. And the Potomac

Abstract

The aquatic weed hydrilla (Hydrilla verticillata Royle) was discovered growing in the Potomac River, south of Alexandria, VA, in Kenilworth Aquatic Gardens, Washington, D.C., and in the Chesapeake and Ohio (C&O) Canal near Seneca, MD. Cultures in Florida of the Kenilworth clone produced male flowers. This is the first report of the occurrence of the male in the U.S. Two distinct isoenzyme patterns have been identified for plants from various locations in the U.S., corresponding to a monoecious strain and a dioecious female. The occurrence of the wild colonies of the monoecious Hydrilla greatly increase the potential for physiological diversity through sexual reproduction, which may have serious consequences for the management of this weed.

Strategies of reproduction, dispersion, and competition in river plants: A review

“…The infestation of the USA by Hydrilla verticillata is another example of weed vegetative reproduction, with only female plants in the Gulf State and California (Spencer & Bowes 1990). The comparison of isozyme patterns of plants of Hydrilla from most known US colonies has shown that all US female strains had identical enzyme pattern, that confirms the role of vegetative reproduction in the invasion (Steward et al 1984;Triest 1991). Vegetative reproduction is often the only method of reproduction even if sexual reproduction exists for the species.…”

A comparison of host range and performance of congeneric leaf-mining flies, Hydrellia pakistanae (Diptera: Ephydridae) and Hydrellia sp., two candidate biological control agents for the South African biotype of Hydrilla verticillata (Hydrocharitaceae)

“…In North America, a female dioecious form was first discovered in Florida in the 1950s (Schmitz et al, 1991) and was later determined to originate in India (Madeira et al, 1997). A monoecious H. verticillata biotype invaded the northern U.S. states (Steward et al, 1984) in the 1970s and was found to be of Korean origin (Madeira et al, 1997). The South African biotype was found to be monoecious and identical to Malaysian and Indonesian H. verticillata (Madeira et al, 2007).…”

Life cycle assessment of nutrient remediation and bioenergy production potential from the harvest of hydrilla (Hydrilla verticillata)

“…Since that time hydrilla has rapidly spread by means of boat trailers and propellers into many lakes, rivers, and reservoirs throughout the U.S. southeast. In addition, a separate strain of more cold-tolerant hydrilla has more recently become established throughout the northern U.S. (Steward et al, 1984;Les et al, 1997). Throughout its introduced range, hydrilla has become notorious for forming dense mats of "topped-out" vegetation that can displace native plants, impede navigation, clog flood control devices, and reduce aesthetic enjoyment of affected aquatic systems (Center et al, 1995;Langeland, 1996).…”