Efficacy and phytotoxicity of herbicides applied for the handling of weeds that infest wheat

Abstract

The objective of this paper was to identify alternatives for the chemical handling of weeds that infect wheat, as well as verifying the phytotoxicity of herbicides on the crop. The experiment was carried out in randomized blocks, organized in a factorial design of 2x 13, with four repetitions. The wheat crops were allocated to factor A (Quartzo and Pioneiro) and the herbicides to factor B (iodosulfuron – 0,100 kg ha^-1; imazapic + imazapyr – 0,140 kg ha^-1; clomazone 0,800 L ha^-1; imazethapyr + imazapic – 1,250 L ha^-1; propanil – 6,000 kg ha^-1; oxyfluorfen – 1,000 L ha^-1; penoxsulam – 0,175 L ha^-1; metsulfuron-methyl – 0,0033 kg ha^-1; 2,4-D – 1,250 L ha^-1; cyhalofop-p-buthyl – 1,380 L ha^-1; pyroxsulam – 0,400 L ha^-1), plus two controls, one weeded and another one infested. Iodosulfuron, propanil, oxyfluorfen, metsulfuron-methyl, 2,4-D, cyhalofop-p-buthyl, penoxsulam and pyroxsulam cause values inferior to 5.5% of phytotoxicity to wheat crops and, in general, they did not differ from the weeded and infested controls. The greatest phytotoxic effects were caused by imazethapyr + imazapic, clomazone and imazapic + imazapyr on the wheat crops. The application of iodosulfuron, imazethapyr + imazapic, imazapic + imazapyr and pyroxsulam presented elevated control percentage of ryegrass, with rates above 95.5%. Imazethapyr + imazapic, clomazone and imazapic + imazapyr presented the greatest phytotoxicity on the wheat crops. Iodosulfuron, imazethapyr + imazapic, clomazone and imazapic + imazapyr and pyroxsulam showed the best controls for ryegrass. Iodosulfuron presented lower influence on the components of wheat grains yield when compared to the other herbicides.