Selectivity index of indaziflam to sugarcane cv. IACSP95-5000 in two soil textures

Abstract

Selectivity index is a way of assessing the discrimination of herbicide to a given crop by observing its effects on the crop and the weeds. The aim was to obtain the selectivity index of indaziflam herbicide to sugarcane cultivar IACSP95-5000 as a function of five weed species in two soils textures. The experiment was carried out in a greenhouse at Piracicaba, São Paulo, Brazil. The treatments consisted of indaziflam doses (0; 12.5; 25; 50; 100; 200; 400; 800 and 1,600 g of the active ingredient (ai) ha-1), applied in pre-emergence of the sugarcane and of the weeds Urochloa decumbens, Urochloa plantaginea, Digitaria horizontalis, Panicum maximum and Rottboellia cochinchinensis. In sandy loam soil, a 100% control for all weeds was provided at 25 g ai ha-1. In clay soil, for D. horizontalis the 90% reduction in total dry mass (ED90) was obtained at 25 g ai ha-1, for R. cochinchinensis at 193 g ai ha-1, for U. plantaginea at 152 g ai ha-1, for P. maximum at 124 g ai ha-1, and for U. decumbens at 94 g ai ha-1. Indaziflam was selective to IACSP95-5000 in both soils, with 10% of reduction in dry mass (ED10) at 137 g ai ha-1 for soil with a sandy loam texture and 353 g ai ha-1 for clay soil. The selectivity index was higher than 1 for all weeds in clay soil. It was not possible to obtain the selectivity index for sandy loam soil due to species susceptibility to the herbicide.