Association between herbicides and sugarcane straw for controlling Urochloa decumbens (Stapf) R. D. Webster in peanuts

Signal grass (Urochloa decumbens) is a common troublesome weed in peanut areas, and its control is essential. This study evaluated the efficacy of herbicides associated with harvested sugarcane residues in controlling U. decumbens. Herbicides were applied with or without sugarcane straw during U. decumbens pre-emergence (imazapic, imazethapyr + flumioxazin, diclosulam, s-metolachlor, clomazone, sulfentrazone, sulfentrazone + diuron, pyroxasulfone, and trifluralin) and post-emergence (imazapic, imazethapyr, bentazon + imazamox, quizalofop-p-ethyl, clethodim, haloxyfop-p-methyl, fluazifop-p-butyl, propaquizafop, and glyphosate). Sugarcane residues reduced plant emergence (68%) and emergence speed (77%). Except for imazapic, every pre-emergent herbicide application without sugarcane straw promoted control levels higher than 90%. The highest U. decumbens control levels (over 95%) occurred mainly with clomazone, pyroxasulfone, and trifluralin, regardless of the straw factor. Glyphosate and haloxyfop herbicides promoted the highest U. decumbens control levels, primarily reducing growth characteristics, followed by propaquizafop, quizalofop-p-ethyl, and fluazifop-p-butyl. The study concluded that sugarcane straw reduced U. decumbens emergence. Clomazone, pyroxasulfone, and trifluralin herbicides applied during pre-emergence promoted the highest U. decumbens control levels, regardless of the presence or absence of sugarcane straw. All pre-emergence herbicide applications without sugarcane straw controlled U. decumbens satisfactorily, except for imazapic. Glyphosate and haloxyfop-p-methyl herbicides applied post-emergence provided the highest U. decumbens control levels, followed by propaquizafop, quizalofop-p-ethyl, and fluazifop-p-butyl, regardless of the presence of sugarcane straw.