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MISCELLANEOUS PUBLICATION NO. 10 65, U.S. DEPARTMENT OF AGRICULTURE 



Sodium arsenite at rates required to control 

 many aquatic weeds is not toxic to fish. But sodium 

 arsenite is highly poisonous to humans and all 

 warm-blooded animals, and extreme caution and 

 attention to details of application are absolutely 

 essential when it is used. It has been used exten- 

 sively since 1930 under rigid State and local regu- 

 lations with few human fatalities or injuries, or 

 serious losses of livestock or wildlife. However, its 

 use is now being generally discouraged in many 

 localities and States. 



Concentrations of ortho dichlorobenzene-xylene 

 mixtures required to control aquatic weeds in ir- 

 rigation ditches will damage corn irrigated with 

 treated water. However, under proper manage- 

 ment, water so treated can be safely used for irri- 

 gation purposes. Copper sulfate usually does not 

 injure bass, bluegill, and certain other fish, but kills 

 trout at concentrations necessary to control algae. 



Copper sulfate is considered safe in drinking water 

 at concentrations up to 3 p. p.m. 



Nematocides 



The principal nematocides in use are halogen- 

 ated hydrocarbons, carbamates, and organophos- 

 phates. Chlorine and bromine residues persist in 

 soil, are taken up by crops, and are a potential 

 hazard to man via foodstuffs and animal products. 

 To date no evidence of injury to man or animals 

 from such residues is known to exist. Although no 

 immediate health hazards are apparent, chlorine 

 accumulation is a factor in tobacco production, 

 and bromine levels above normal are reported in 

 milk from cows fed fodder grown on nematocide- 

 treated land. Runoff from fields treated with nema- 

 tocides and irrigation water to which nematocides 

 have been added are potential hazards as pollut- 

 ants. 



