Controle em pós-emergência de Conyza spp. em soja Enlist®

Abstract

Conyza spp., stand out as the main weeds in soybean in the state of Mato Grosso do Sul, and there are reports of biotypes resistant to EPSPS (5-enolpyruvylshikimate-3-phosphate) and ALS (acetolactate synthetase) inhibitor herbicides, making to difficult to manage. However, 2,4 D-tolerant soybean (ENLIST®) presents new possibilities for herbicide positioning. In view ofthe above, the objective of this work was to evaluate the effects of the association of 2,4D withother post-emergent herbicides with different mechanisms of action, in single and/or sequential applications, in the control of Conyza spp. and the selectivity of these treatments in the soybeancrop. The experiment will be conducted in the field, at the FAECA (Experimental Farm of Agricultural Sciences) of UFGD (Federal University of Grande Dourados), coordinates at 21º 57’ south latitude and 46º 51’ west longitude, the experimental design of completely randomized block, with four repetition, with 2,4D-tolerant soybean (B5595CE). The treatment that will be used are: 2,4D + glyphosate (1020 +1250 g ha-1 ); 2,4D + chlorimuron+ glyphosate (1020 +15 + 1250 g ha1 ); 2,4D + cloransulam + glyphosate (1020 + 33,6 + 1250 g ha-1 ); 2,4D + imazethapyr + glyphosate (1020 + 100 +1250 g ha-1 ); 2,4D + bentazon + glyphosate (1020 + 720 +1250 g ha-1 ); 2,4D + imazamox + glyphosate (1020 + 42 + 1250 g ha-1 ), in each of these treatments will be performed in a single application. In contrast the treatments: 2,4D + glyphosate (1020 +1250 g ha-1 ); 2,4D + chlorimuron + glyphosate (1020 +15 +1250 g ha-1 ); 2,4D + cloransulam + glyphosate (1020 + 33,6 + 1250 g ha-1 ); 2,4D + imazethapyr + glyphosate (1020 + 100 +1250 gha-1 ); 2,4D + bentazon + glyphosate (1020 + 720 +1250 g ha-1 ); 2,4D + imazamox + glyphosate (1020 + 42 + 1250 g ha-1 ) these treatments will be receiving an sequential application 15 days after the initial application (DAI) of glufosinate, ammonium salt (500 g ha-1 ) and two more controls without herbicide application the compare to the others treatments, with and without weeding. Control of weeds and phytotoxicity of the soybean crop were evaluated at 7, 14, 21, 28 and 35 days after the first application of treatments (DAT). Were realized weight analyzes (1000 grains), productivity (kg ha-1 ) and grain moisture content testing. Statistical analysis was performed using the GAMLSS model with beta distribution. The results were submitted to analysis of variance by the F test, comparing the treatment levelswith the Tukey test. All statistical analyzes were performed with the R software. Regarding phytotoxicity, all treatments were not very expressive, being less than 15%. For the control dataof Conyza spp. only at 21 DAT the treatments with sequential application showed satisfactory results, greater than 80%. Herbicide associations with 2,4D when applied in a single application are not an option for the control of Conyza spp. in post-emergence. Sequential applicationsincrease the control percentages, in this situation we have a satisfactory level.