as low as 0.6 p. p.m. late in the growing season. These treatment rates 

 give adequate control and are well below the maximum concentration of 

 3.0 p. p.m. of copper ion or 7.5 p. p.m. of copper sulfate in potable water 

 supplies, as established by the U.S. Public Health Service. 



In Ponds and Lakes 



(1) For control of rooted submersed species in still water : Sodium 

 arsenite at 3 to 4 p. p.m. will give adequate control for usually all, or 

 most, of one growing season. For treating localized areas along the shore- 

 line of a lake, concentrations of 6 to 10 p. p.m. may be necessary for ade- 

 quate control because of diffusion into untreated areas. 



Comments and precautions .- -Arsenical compounds are recognized 

 poisons and must be handled with extreme care to avoid injury or death 

 to human beings, livestock, or game animals. Wash application equip- 

 ment and empty containers thoroughly with water after each use. Wear 

 goggles during spray application and wash hands thoroughly afterward. 

 Delay use of treated water for bathing, swimming, lawns, gardens, or 

 animals for 3 days. Do not use the arsenical treatment in any waters 

 intended for use in rice culture. Carefully observe all State laws on 

 applications of arsenicals. 



Fish are not killed by concentrations of sodium arsenite below 1 1 to 

 12 p. p.m., which are in excess of the concentrations recommended for 

 aquatic weed control. 



(2) For control of rooted species (such as parrotfeather, waterweed, 

 coontail, pondweeds, and naiad): 2,3-dichloro- 1 , 4 -naphthoquinone (dichlone) 

 at 10 to 20 pounds per surface acre. At these rates, concentrations of the 

 chemical in treated water range from 2.7 p. p.m. to 10.8 p. p.m. in water 

 5 to 10 feet deep. Toxicity of dichlone to fish has been variable and safe 

 concentrations have not been definitely determined. 



(3) For control of blue-green algae : Dichlone at 1 pound per surface 

 acre of water has given effective control without injury to higher aquatic 

 life, fish, or zooplankton. Repeated applications usually are necessary to 

 maintain control. 



(4) For control of filamentous green algae : Copper sulfate at 0.5 to 

 1.0 p. p.m., or RADA at 0.3 to 1.0 p. p.m. 



EMERGENT AND MARGINAL WEEDS 



(1) For control of cattails and bulrushes : (a) Low-volatile ester of 2,4-D 

 at 4 to 6 pounds in a l-to-20 oil- water emulsion for a total volume of 150 

 to 300 gallons per acre applied as a foliage spray. The first spray treat- 

 ment should be made just before heading stage of the weeds and repeated 

 as necessary on regrowth. About 3 applications over a 2-year period are 

 necessary for complete control of these weeds, (b) Dalapon at 10 to 20 

 pounds per acre or amitrol at 6 to 10 pounds, applied at the preheading 

 or early heading stages. Addition of 5 to 10 gallons of oil per acre to the 

 spray solution greatly improves results in most situations. Repeated 

 applications may be necessary. These treatments are more expensive 

 than the 2,4-D treatment, but are safer to use near crops extremely 

 sensitive to 2,4-D, such as cotton, grapes, and tomatoes. Reasonable care 

 should be used, however, to prevent herbicide treatments from drifting to 

 crop plants. 



(2) For control of water lilies, lotus, spatterdock, arrowhead, pickerel- 

 weed, spikerush, and smartweed : 2,4-D at 1/2 to 2 pounds per 100 gallons of 

 diesel oil in sufficient volume to thoroughly cover foliage. 



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