Invasive Weed Spraying Control Program Starts April 2nd in the Palo Verde Area

Media Contact: Jack Simes, 928-343-8334

For Release: March 02, 2007

On April 2, the U.S. Fish and Wildlife Service will begin applying aquatic pesticides in the Palo Verde Irrigation District's outfall drain. This control measures helps prevent the spread of Giant Salvinia (Salvinia molesta), a highly invasive non-native aquatic weed from Brazil. The spraying program will start from the Palo Verde area on the California side of Walter's Camp and up to the confluence with the Colorado River.

As part of a comprehensive multi-agency effort to control this weed's infestation in the Lower Colorado River and associated backwaters, spraying is scheduled to continue through October 2007. This weed can damage irrigation systems and waterways so the program was implemented to help avoid its proliferation downstream.

Pesticides being used in the program 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.

Described as "the world's worst weed," Biologists discovered it here in the lower Colorado River in the summer of 1999. The plant is very invasive, and under the right conditions 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 the effort to control and eradicate this plant from the lower 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

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