As part of a multi-agency comprehensive effort to control the infestation of giant salvinia in the Lower Colorado River and associated backwaters, the U.S. Fish and Wildlife Service is applying aquatic pesticides in the Palo Verde Irrigation District's main drain, including the Palo Verde area, and in the Colorado River channel on the California side of the Walter's Camp area. Application of the pesticides began on September 27, 2004, and is scheduled to continue through October 9, 2004.

The pesticides are being applied in an effort to control giant salvinia (Salvinia molesta), a highly invasive non-native aquatic weed, to prevent damage to irrigation systems and waterways, and avoid proliferation of the weed downstream.

The pesticides include diquat dibromide (Reward), glyphosate [N-(phosphonomethyl) glycine, isopropylamine salt] (Rodeo), and copper carbonate (CuCO3) (Clearigate). According to manufacturer's label, humans and domestic animals should not drink or swim in water treated with diquat or glyphosate for one day after treatment. Copper herbicides have no use restrictions or precautions.

Giant salvinia, described as "the world's worst weed," is an aquatic fern from Brazil which was discovered by biologists in the Lower Colorado River in the summer of 1999. The plant is very invasive; under the right conditions, it multiplies rapidly, threatening recreation use of infected waters, fishing areas, irrigation water delivery, hydropower production, endangered species, and sensitive habitats.

The Bureau of Reclamation is leading a multi-agency effort to control and eradicate this plant from the Colorado River. The Lower Colorado River Giant Salvinia Task Force also includes the Bureau of Land Management, U.S. Fish and Wildlife Service, Arizona Game and Fish Department, California Department of Fish and Game, and other state and local entities; a complete listing can be found on the Task Force's web site at at http://ag.arizona.edu/azaqua/salvinia/salviniahome.htm