Seletividade do herbicida tembotrione em genótipos de cana-de-açúcar no sistema de mudas pré-brotadas

Abstract

The application of herbicides in post-planting of pre-sprouted sugarcane seedlings stands out in the control of weeds in the crop, with effectiveness in eradicating them in a short period. However, phytotoxicity effects to herbicides may occur, depending on the variety of sugarcane, time of application and doses of the products. Thus, there is a need for research aimed at identifying new active ingredients that are efficient in controlling weeds and that present selectivity for the cultivation of sugarcane.The objective of this study was to evaluate the selectivity of the herbicide tembotrione over genotypes of sugar cane in doses and times of application in the pre-sprouted seedling system. The experiment was divided into two stages: In the first stage, the effect of doses of the herbicide tembotrione + mineral oil (0; 50.4; 75.6; 100.8; and 126 g ia ha-1+ 108 g ia ha-1, respectively), on application times; 0, 20 and 40 days after transplanting. In the second stage, the application of 75.6 g ia ha-1of theherbicide tembotrione + 108 g ia ha-1of mineral oil was evaluated on four sugarcane genotypes: RB966928, RB855156, RB93509 and IACSP95-5000. During the conduction of the two stages, phytotoxicity assessments were carried out at 7, 14, 21 and 28 days after application and at the end the number of tillers, shoot fresh matter and shoot dry matter was determined. It was found that the herbicide tembotrione, when applied in smaller doses and in initial periods of the culture in post-emergence, presents selectivity for the varieties RB867515, RB966928, RB855156, and RB93509, however, it provides decrease in the accumulation of shoot dry mass on the IACSP95-5000 variety.