Abstract
Registered herbicides for use in sugarcane, ametryn, diuron, asulam, hexazinone, metribuzin, non-registered terbutryn, pendimethalin, and imazapyr were evaluated to control itchgrass (Roftboellia exaltata) in sugarcane in field experiments at the Lajas Substation with plant and ratoon crops. Imazapyr, together with pendimethalin, terbutryn and ametryn, provided good itchgrass control in the plant crop, comparable to the hand weeded treatment. In the ratoon crop most herbicides used showed good control, though the Roftboellia population before herbicide application was much lower than for the plant crop. Imazapyr caused chlorosis in sugarcane shoots; chlorosis was more severe in the ratoon crop. These herbicides at the recommended rates of 0.28, 1.78, 2.69 and 4.49 kg/ha, respectively, produced sugar yields ranging from 14.92 to 17.02 tons/ha that were statistically not different from those of the hand weeded plots (17.59 tons/ ha) but significantly higher than those of the diuron, asulam and the unweeded check plots in the plant crop. The combined plant and ratoon crop for sugar production for pendimenthalin (1.78 kg/ha) was as good as for the hand weeded plots, but not statistically better than the rest of the herbicide treatments, except for hexazinone and imazapyr.