RESPONSES OF SOME SUGARCANE VARIETIES TO STANDARD AND COMBINATION RIPENER TREATMENTS
The effects on sucrose yield of varying the time interval between Ethrel and Fusilade Super applications in a com­ bination treatment were tested on variety NC0376. Results suggested that Ethrel applied 12 weeks, and Fusilade Super applied eight weeks before harvesting were the most bene­ ficial. Other varieties which responded to a combination treatment were N19, N12 and N22. Varieties N14, N19, N17, N12, N22 and NC0376 grown under irrigation all re­ sponded to one of the ripener treatments, and their responses to Ethrel and Fusilade Super are discussed. There were no significant gains in sucrose yield of CP66/1043 in response to the ripeners although sucrose content was increased.
Drought Stress Reduces Fluazifop-P Activity on Green Foxtail (Setaria viridis)
Although drought-stressing green foxtail before and up to 1 d after herbicide application did not reduce control with fluazifop-P in growth chamber trials, extending the drought stress for 2 to 4 d after herbicide application reduced control of green foxtail with fluazifop-P by 40 and 57%, respectively. Absorption and translocation of 14C-fluazifop-P 1, 4, and 10 d after herbicide application were similar between nonstressed and drought-stressed plants. Drought-stressed green foxtail converted slightly more of the parent acid of fluazifop-P to polar conjugates 4 d after herbicide application than did nonstressed plants, but these differences in metabolism were probably not adequate to explain large differences in efficacy.
Residual effect of glyphosate as a ripener on sugarcane.
The effect of a low dosage of glyphosate in raising the juice purity and sucrose content of unstressed sugarcane 'stalks is well documented. The residual effect of the ripener on the succeeding crop of cane grown under favourable conditions has been shown to be short-lived, seldom influencing yields. The low residual activity of glyphosate was confirmed in several trials grown under optimum moisture conditions. In one large trial in which three successive crops were sprayed no evidence of a residual effect on yield was found. Yields were, however, increased considerably by the ripening effect of glyphosate. In three rainfed trials affected by drought, yields were reduced by 11 to 17% due to the application of glyphosate on the preceding crop. The decrease in yield in some varieties was much greater than in others. Varietal differences could be attributed to the different sensitivities of varieties to drought rather than to glyphosate per se. It is recommended that glyphosate be used only where cane is not stressed or likely to be stressed between the time of spraying and harvesting.