81 



Table 3-4. Costs comparison for the use of a combination of GA3 and 



2,4-D compared to normal application rates of 2,4-D for the 

 control of waterhyacinths on the St. Johns River, Florida. 



Option A: Normal rate of 2,4-D (2.24 kg/ha) 



1982 2,4-D costs 1= $3.32/kg x 2.24 kg/ha = $7.44/ha 



Annual costs = $7.44/ha x 3642 h/yr 1= $27,096/yr 



Option B: 8.0 g/ha GA3 and 0.10 of normal application rate of 

 2,4-D (0.224 kg/ha) 2 



1982 2,4-D costs = $3.32/kg x 0.224 kg/ha = $0.75 



1982 GA3 costs 3 = $1.14/g x 8.0 g/ha = $9.12 



Total $9.87/ha 



Annual costs = $9.87/ha x 3642 ha/yr = $35,947/yr 



Option C: 23.5 g/ha GA 3 and 1.12 kg (a.e.)/ha 



1982 2,4-D costs = $3.32/kg x 1.12 kg/ha = $ 3.72/ha 



1982 GAo costs = $1.14/g x 23.5 g/ha = $26.79/ ha 



J Total $30.51ha 



Annual costs = $30.51/ha x 3642 ha/yr = $111, 117 /yr 



1. Current bid price (McGehee, 1982). 



2. Pieterse and Roorda (1982). 



3. Current market price (Asgrow Florida, Inc.). 



4. Lowest rates which produced a level of control which was not 

 significantly different from 2,4-D at 2.24 kg/ha (see Table 3-2) 



