CHEMICAL CONTROL OF BROADLEAF WEEDS IN GRAIN SORGHUM

Abstract

Ineffective weed control is an important problem in grain sorghum (Sorghum bicolor L. Moench) production in northern Tamaulipas,México. Several options for chemical weed control in sorghum in pre-(PRE) and post - emergence (POST) were evaluated under field conditions in 2007 and 2008. Atrazine and amicarbazone 750 g ha^-1 applied PRE resulted in good control of wild sunflower (Helianthus annuus L.) and Palmer amaranth (Amaranthus palmeri S. Wats), without causing damage to sorghum plants. Among herbicides applied POST to six-leaves sorghum, prosulfuron 17 g ha^-1 showed excellent control of wild sunflower in both years, however Palmer amaranth control was only regular in 2008 and it did not control silverleaf nightshade (Solanum elaeagnifolium Cav.) in any year. The mixture of carfentrazone 2.5 g ha^-1 + 2, 4-D 225 g ha^-1 and 2, 4-D to 720 g ha^-1 showed regular weed control, but damage was caused in sorghum reducing grain yield. Dicamba at 144 g ha^-1 resulted in a similar weed control to 2, 4-D but with less damages to sorghum and without reducing its yield. Bromoxinil 480 g ha^-1 effectively controlled wild sunflower and Palmer amaranth but had no effect on silverleaf nightshade. Bentazon at 960 g ha^-1 controlled wild sunflower, but it was ineffective on Palmer amaranth and on silverleaf nightshade. Results indicate that there are several options for the control of wild sunflower and Palmer amaranth, while silverleaf nightshade must be controlled by adding a POST hormonal herbicide such as 2, 4-D or dicamba.