AbstractField trials in 1986-87 were conducted in the humid sugarcane growing area of San Germán and under irrigation at the Lajas Research and Development Center to evaluate several candidate herbicides for controlling itchgrass (Rottboellia exaltata L.f.) in sugarcane fields. Terbutryn [2—(Tert— butylamino)—4— (ethylamino)—6— (methylthio— S—triazine] at 2.68, 5.35 and 10.70 kg/ha as a direct post emergence application over itchgrass 15 to 20 cm tall provided excellent grass control with no injury to the crop. Asulam [methyl (4 amino phenyl) (sulfanyl)] carbamate at 2,09 kg/ha showed a slow short-term action. With Terbutryn at 10.7 kg/ha and the hand-weeded check plots significantly higher cane and sugar yields were obtained, Pendimethalin [N—(ethylpropyl)—3,4—dimethyl—2,6—dinitroben— zenamine] at 3.56 kg/ha as a preemergence soil-in corpora ted application to a primavera sugarcane crop was effective in controlling itchgrass. A single application of this product at 1.78 kg/ha was markedly less effective. Imazapyr (2-[4,5 dihydro—4—methyl—4—(l-methylethyl)—5—0x0—lH—imidazolzyl]— 3—pyridinecarboxylic acid) with 2—propanamine (1:1) salt at 0.125 and 0.25 kg/ha controlled of itchgrass excellently. Combinations of pendimethalin and imazapyr were effective in controlling grass weeds. The best cane tonnage and sugar yields were obtained from the hand-weeded plots and from combinations of pendimethalin and imazapyr. With pendimethalin at 0.89 and 1.78 kg/ha and asulam at 2.98 kg/ha there was very little effect from the herbicide treatments on increasing yield.
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