The weed flora infesting sugar cane fields is specific and well characterized. The continuous use of the same hebicide is one of the crop managing factors which has mostly contributed to this weed selection. The purple nutsedge (Cyperus rotundus) is one of most important weed species infesting sugar cane fields. The objective of this studv was to evaluate the efficiency of the chemical control of purple nutsedge bv the herbicide halosulphuron, a sulphonylurea, ln the sugar cane crop. The experiment was set up at the EPAMIG Experimental Station, Prudente de Morais - MG, March 24, 1994, with the variety RB-72454, in a humic-glev silt-clay lowland soil, pH 5.8 and 2.9 organic matter. The experimental lavout was a randomized block design, with six tratments and five replications. The herbicides halosulphuron and 2,4-D (control) were applied as post-emergence, covering the whole area (sugar cane plants were 65cm tall), with a hand-held, 2,4kgf/cm2 constant pressure spraver, with two 110.03 flat spray tips, at the rate of 260 l/ha. During herbicide application, 15-30cm high purple nutsedges were terminating their vegetative growth and begining to flower. Halosulphuron was applied in a mixture wlth a Tallow Amine surfactant, 0.5% v/v. Weed control evaluation were done at 15, 30, 60 and 90 days after herbicide application, couting the number of live sproutings ln 0.2m2/plot . Results showed that halosulphuron, at the rate of 131,25 g i.a./ha gave better than 90% weed control 90 days after application. Viability tests performed in tubers collected 20cm deep, 90 days after herbicide application, showed that halosulphuron rates of 93,75; 112,5 and 131,25 g i.a./ha reduced viable tubers by 47,7%, 52,7% and 60,7% respectively. These results are significantlv better than those obtained with 2,4-D, which reduced viable tubers by only 23%. Halosulphuron appeared to be selective to sugar cane when applied in post-emergence covering the hole area, showing no injury svmptoms such as necrosis or stunted growth.
Saccharum spp; Cyperus rotundus; 2,4-D