Controle químico de biótipos de azevém

Abstract

Currently the ryegrass (Lolium multiflorum) has been established as a major weed in several crops. More recently rice farmers have faced problems in dry areas before sowing the irrigated rice where this species is present, using it for the herbicide glyphosate. The objective of this work was to evaluate alternatives to chemical control of ryegrass biotypes. Two experiments were conducted in a greenhouse, in completely randomized design, with three replications. The first experiment was arranged in factorial 5 x 2, factor A being composed of increasing doses of glyphosate (0; 1080; 2160; 3240 and 4320 g e.a. ha-¹ ) and the factor B by ryegrass biotypes, A (suspected resistance to glyphosate) and B (susceptible to glyphosate). The second experiment was arranged in factorial 11 x 2, factor A was composed of herbicides, cyhalofop-p-buthyl; amonio-glufosinate; haloxyfop-p; imazapic + imazapyr; paraquat; penoxsulam; profoxydim; propanil; propanil + thiobencarb; sethoxydim; and the control treatment without herbicide application, and factor B composed of ryegrass biotypes, A (suspected resistance to glyphosate) and B (susceptible to glyphosate). The evaluations were performed to control 14 days after treatment application (DTA) the first experiment and 28 DAT for the second, and the dry mass of shoots (MSPA) held at 28 DAT for both experiments. The results showed that the chemical control of ryegrass with the use of glyphosate did not differ between biotypes A and B, where doses of the herbicide from 1080 g ha-1 promoted total plant control. The herbicides paraquat, amonio-glufosinate, imazapic + imazapyr, cyhalofop-p-buthyl, sethoxydim, profoxydim and haloxyfop-p effectively control the biotypes evaluated, can be recommended as alternatives to control ryegrass in irrigated rice fields.