Weed management in cotton

Abstract

The weeds are becoming a major challenge for cotton production across the world, and the crop is infested by broad leaves, grasses, and sedges. Although the presence of weeds is deleterious for potential yield, the extent of losses depends on weed type, density, duration, and crop growth stage. Some weeds like Datura stramonium L., Amaranthus palmeri L., Amaranthus retroflexus L., and Ambrosia trifida L. cause significant yield losses at very low densities in comparisonwith Cucumismelo L. and Eleusine indica L. The cotton crop is very sensitive at early growth stages where weed presence during the first 2 months of growth may reduce yield from 10%to 90%. The most common effects of weeds on cotton quality are higher trash contents and lint staining problem. The various weed control options have been used for weed management in cotton; however, the efficacy of weed control methods remains low, probably by practicing weed control out of the critical period of weed-crop competition and selection of inappropriate method. The cost of weed control ranges from 54.5 to 320.6 US$ ha-1 in various cotton-growing countries of theworld. The use of herbicides for weed control is common in the world; however, excessive and non-judicious use of herbicides led to the evolution of resistant weed biotypes. It provided the basis for development of glyphosate-tolerant cotton genotypes. The big change has been made for weed management with the advent of genetically modified glyphosate-tolerant cotton. It offers flexibility in herbicide use and time of application and improves weed control efficiency and economic returns. The evolution of herbicide resistance has been reported in Amaranthus palmeri L., Commelina benghalensis L., Conyza bonariensis L., Conyza canadensis L., and Sorghum halepense L. Some new technologies like Roundup ReadyXtend cotton and Enlist technology are being developed to cope to the challenge of glyphosate resistance.