RESPOSTA DO CAPIM JIGGS (Cynodon dactylon) A DIFERENTES FORMULAÇÕES COMERCIAIS DE CLETODIM

Abstract

Grasses belonging to the genus Cynodon sp. are widely used in tropical and subtropical climates. The species exhibits versatility in use, being suitable for grazing systems and efficient in hay and silage production, as well as in intercropping with other forage species. However, the presence of weeds in pasture areas can cause deleterious effects, resulting in losses for the development of forage species. The hypothesis was that different commercial formulations of the herbicide clethodim could present distinct levels of phytotoxicity and selectivity to Jiggs grass. Thus, given the lack of studies and management practices for weed control in Jiggs grass, the objective of this work is to evaluate the tolerance of the grass to different commercial formulations of the active ingredient clethodim. The experiment was conducted in the field at the Instituto Federal Goiano – Campus Urutaí, in a randomized block design with five treatments and five replications. The treatments consisted of: (T1) Control, (T2) Grasidim®, (T3) Select 240 EC®, (T4) Freno 240 EC®, and (T5) Cletodim CCAB 240 EC®, applied at a dose of 101.6 g a.i. ha⁻¹. Phytotoxicity was evaluated at 7, 14, 21, and 28 days after application (DAA), average temperature was assessed using aerial thermal images, and shoot dry matter (SDM) was evaluated at 28 DAA. Data were subjected to analysis of variance, and means were compared using Tukey's test. For phytotoxicity, a significant interaction was detected between the formulations and the days after application, with the different formulations promoting distinct evolution of phytotoxicity symptoms throughout the evaluation period. Grasidim® showed lower average levels of phytotoxicity and greater dry matter accumulation, indicating greater selectivity to Jiggs grass. In contrast, Select 240 EC®, Freno 240 EC®, and Cletodim CCAB 240 EC® promoted higher average injury levels, with Select 240 EC® and Cletodim CCAB 240 EC® also reducing biomass more significantly. It is concluded that commercial clethodim formulations differ in their selectivity to Jiggs grass, with Grasidim® standing out as the most tolerated under the evaluated conditions.