2 

 for disease vectors (Webber, 1897; Penfound and Earle, 1948; Hitchcock 

 et al., 1949; Seabrook, 1962; Anonymous, 1965; Bock, 1966; Buker, 1982.) 



Prior to 1946, waterhyaci nth control operations consisted of 

 mechanical operations utilizing various conveyor, chopper or shredder 

 machines; containment apparatus such as floating booms, fences or traps; 

 pusher boats to assist the plants to salt water; and the use of various 

 inorganic chemicals such as sodium arsenite (Webber, 1897; Brown et al . , 

 1946; Penfound and Earle, 1948; Hitchcock et al . , 1949; Bock, 1966; 

 Wunderlich, 1967; Buker, 1982). Large-scale control of waterhyaci nths 

 was revolutionized in the mid-1940 1 s by the discovery of the herbicidal 

 properties of 2,4-dichlorophenoxyacetic acid (2,4-D). Since its 

 development, various formulations of 2,4-D have been routinely utilized 

 for control of waterhyaci nths (Anonymous 1946; Brown et al . , 1946; 

 Hildebrand, 1946; Hitchcock et al . , 1949; Penfound and Earle, 1948). 

 Currently, dimethylamine salt is the only formulation of 2,4-D labeled 

 by the United States Environmental Protection Agency (EPA) for use in 

 public waters which are either flowing and/or potable water supplies. 

 During 1981, governmental agencies in Florida applied approximately 

 63,700 kg of 2,4-D to public waters for control of nuisance aquatic 

 vegetation, the majority of which was waterhyaci nths (Dupes and Mahler, 

 1982). 



Increased public awareness, spurred by the environmental movement 

 and adverse publicity associated with the military's use in Vietnam of 

 the defoliant, "Agent Orange", which was a combination of 2,4-D and 

 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), has caused various regula- 

 tory agencies to more closely scrutinize labeling of new herbicides and 

 to review existing registrations of herbicide products currently 



