39 

 Engineers, Jacksonville District, applies these latter rates of 2,4-D 

 under a control program which maintains the waterhyaci nth population at 

 a minimum non-problematic level (Joyce, 1977). This approach has 

 reduced by 50 percent the quantity of herbicide utilized annually on the 

 St. Johns River, Florida, for waterhyaci nth control (McGehee, 1982). 



