St. Johns River, Florida, with combinations of GA~ at 0.0, 23.5, 47.0, 

 and 94.0 g/ha and 2,4-D at 0.00, 0.56, 1.12, 2.24, and 4.48 kg/ha. 

 Effects of treatment rates were recorded as percent change from initial 



biomass and initial number of plants. Effects of GA 3 on the transloca- 



14 

 tion of " C labeled 2,4-D were monitored through time for levels of 



14 14 



C per milligram of plant tissue and percent of total C translocated 



to separate plant parts. 



Regression analysis indicated the lack of significant interaction 



between GA3 and 2,4-D in terms of increased efficacy of 2,4-D above 



routine application rates of 2.24 kg/ha. Additive effects of 2,4-D and 



6A3 were suggested, however. Costs analysis of various combinations of 



GA3 and 2,4-D indicated that addition of GA3 in order to lower rates of 



2,4-D would increase waterhyaci nth control costs by over 300.0 percent. 



14 

 Translocation of " C-labeled 2,4-D to meristematic waterhyaci nth 



tissues was not increased due to pretreatment with 100 mg/1 GA3. 



Increased translocation to leaves other than 2,4-D treated leaves was 



suggested. Use of GA3 to significantly reduce rates of 2,4-D used to 



control waterhyaci nths under field conditions was not justified from either 



an increased efficacy or economic standpoint. 



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