Efficacy of two Formulations of Clethodim on Grass Control and its Antagonism with Bentazon

Abstract

The objectives were to evaluate the efficacy of Icasso 24 EC and Arrow 12 EC, two commercial formulations of the herbicide Clethodim, and to determine the antagonism between Clethodim and Bentazone. In two trials, grass weed control and phytotoxicity to dry bean were evaluated; in another trial, the antagonism was evaluated, by mixing the two formulations of Clethodim (120 g of active ingredient per hectare) in the tank with Bentazone (1,440 g of active ingredient per hectare). All applications were made with a stainless steel backpack sprayer, model T pressurized with CO2 at 35 psi, a 2 m wide boom, with four flat fan nozzles spaced 50 cm between them. A completely randomized blocks design was used. In all the trials, data from the controls without herbicide applications were not used in the statistical analysis. The mean separation of results was established with Duncan test at 5%. In the first trial, at 2 weeks after application, the formulation Icasso 24 EC had 86% control and Arrow 12 EC had 73%, both were applied at 96 g of active ingredient per hectare. In the second first trial, at 3 weeks after application, using 96 g of active ingredient per hectare, the control with Icasso 24 EC was 40% and with Arrow 12 EC 33%, increasing the rate to 120 g of active ingredient per hectare weed control was 45% with Icasso 24 EC and 36% with Arrow 12 EC. The control was better with Icasso 24 EC, than with Arrow 12 EC, therefore, the difference in weed control is attributed to the formulation of the herbicides, since manufacturers add different inert ingredients that enhance the efficacy of the herbicide. No phytotoxicity to dry bean was observed in any of the experiments. This indicates that none of the formulations nor inert ingredients caused damage to the dry bean. A factorial design was used for the antagonism evaluation, statistical differences were found between formulations and when the formulations were applied alone or mixed with Bentazone. In all evaluations there was no interaction, which indicates that the factors (formulation and mixing with Bentazone) act independently. At 3 weeks after the application, of the mixture of Icasso 24 EC with Bentazone, control was reduced from 74 to 25%, a reduction of 66%. When mixing Bentazone with 12 EC Arrow the control was reduced from 60 to 11%, a reduction of 82%. Based on these results it is concluded that Bentazon is antagonistic to both formulations of Clethodim, and there is a greater antagonist or reduction in the control with Arrow 12 EC than with Icasso 24 EC.

Ceiba, 2012. Volumen 53(1):57-64