78 

 viable and retained the ability to reinfest the plot. For this reason, 

 the percent change in number would appear to be a more realistic 

 estimator of efficacy. 



According to the Waller-Duncan multiple range test, there was no 

 significant difference in the mean change in weight or number between 

 the three treatment rates of GA 3 (2,4-D rate = 0.00 kg/ha). There was a 

 signficant increase in the mean weight change of the three levels of 

 GA 3 (2,4-D rate = 0.00 kg/ha) when compared to the control plot; how- 

 ever, the GA 3 treatments did not affect the mean number of plants per 

 sq m when compared to the control plot. Tables 3-1 and 3-2 indicate that 

 there were no significant (a=0.05) increases in the efficacy of any 

 fixed rate of 2,4-D when combined with any of the four levels of GA 3 . 



Table 3-3 presents the results of the large scale application of 2,4-D 

 and gibberellic acid to a dense stand of waterhyaci nths. Twenty-four days 

 post- treatment, plot 3, which received 2.24 kg/ha 2-4-D, and 0.0 g/ha GA, 

 had the highest percentage (80.40) of dead waterhyaci nth plants per 

 transect. The next highest percent dead plants was plot 2 which received 

 0.84 kg/ha 2-4-D, and 94.1 g/ha GA, with 34.70 percent, followed by plot 



1 which received 0.84 kg/ha 2-4-D, and 0.0 g/ha GA, with 24.20 percent 

 dead plants per transect. The proportions of dead plants in plots 1 and 



2 were not significantly different from each other at a=0.05; however, 

 the proportion of dead plants in plot 3 was significantly different from 

 plots 1 and 2 at a=0.05. A visual inspection of the phase two plots was 

 conducted 63 days post- treatment. Quantitative evaluations were not 

 possible due to disturbance of the plots by wind, currents, and the 

 24-day post- treatment sampling procedure. However, the visual evalua- 

 tion did indicate that the waterhyaci nth populations in plot 3 had been 



