Controle de tiririca (Cyperus rotundus) e efeito residual sobre a cultura do feijão do herbicida Imazapyr

Abstract

The objective of this research was to study rates of the herbicide imazapyr for purple nutsedge (Cyperus rotundus) control in lowland soils and to determine the carryover period for dry beans (Phaseolus vulgaris), cv Carioca, grown at different timings after the herbicide application. The experiment was carried out at EMBRAPA/CNPMS, in Sete Lagoas, MG, Brazil, and the effect of imazapyr on purple nutsedge was evaluated spraying at three rates: 375, 750 and 1500 g ha-1, broadcast application at the 4-5 leaf crop stage. Seven purple nutsedge control evaluations were recorded at 14, 35, 56, 70, 77, 84 and 91 days after application (D.A.A.). For the carryover study the treatments consisted of the same previously applied rates of imazapyr and eight application periods before crop sowing (98, 84, 63, 42, 28, 21, 14 and 7 days - D.B.S.). A satisfactory control of purple nutsedge was obtained with imazapyr, except for the rate 375 g ha-1, which controlled purple nutsedge n for 35 days. The higher rates were able to keep purple nutsedge under control for 70 days. As the rates of imazapyr increased, more phytotoxic effects were observed in dry bean plants. More severe damage to the crop was observed when the herbicide was applied closer to crop seeding, resulting in yield losses. The lowest imazapyr rate (375 g ha-1) applied at 98 DBS, caused small injury to the crop, without yield losses.