Alternatives for chemical control of rice flatsedge resistant to ALS-inhibiting herbicides

Abstract

Cyperus iria L. (CYPIR) is one of the main cyperaceae occurring in irrigated rice crop. For many years, acetolactate synthase inhibitor herbicides (ALS) were the main tool to control CYPIR, favoring the selection of cross-resistance biotypes. Based on the level of resistance, it is necessary to adopt alternative chemical control measures in order to avoid the evolution of the resistance and to reduce the interference on the crop. The aim of this work was to evaluate alternatives of chemical control of CYPIR to ALS-inhibiting herbicides, occurring in irrigated rice crops in southern Brazil. There were conducted two experiments in greenhouse, arranged in completely randomized design with four replicates. The herbicides used were: imazethapyr; imazapyr+imazapic formulation; bentazon; propanil; formulation of bentazon+imazamox; mixture of (bentazone + imazamox) + (imazapyr + imazapic); association of bentazone + (imazapyr + imazapic); glyphosate; and control without herbicide. The control evaluation was performed in a resistant (CYPIR-S) and susceptible (CYPIR-S) biotype, and the phytotoxicity evaluated in the Guri Inta CL, IRGA 424 RI and IRGA 409 cultivars. At 28 days after application (DAA) the control / phytotoxicity and shoot dry matter (SDM) were evaluated. All treatments tested, except for imazethapyr and imazapyr+imazapic applied in isolation, were efficient. There are alternatives to the chemical control of Cyperus iria resistant to ALS-inhibiting herbicides and these, when associated with products that have different mechanisms of action, do not impair the use of ClearField® technology.