Weeds control by chemical method, aiming balance shifting of the agro-ecosystem in favor of cultivated crop, which proved to be relatively more efficient and economical. The efficacy of herbicides, however, depends more upon their formulation in addition to time, methods and rates of application . It was concluded from an experiment that hand weeding and mixture of herbicides Puma super 75 EW and Buctril-M 40 EC showed better results for controlling winter weeds . while evaluating 5 post-emergence herbicides alone at recommended doses and in combination with DMA-6 for weed control in wheat concluded that herbicide application suppressed weed population effectively. Dosanex + DMA-6 and Arelon provided the best weed control. However, Dicuran M.A. 60 WP + DMA-6 produced the maximum grain yield. DMA-6 alone and in combination with Dicuran M.A. 60 WP was more economical than all other herbicidal treatments. investigated the effect of different graminicides used at varying levels and concluded that lesser dose of Topik15WP is required for the control of wild oat as compared to Puma Super 75 EW. The maximum weed efficiency was noted for Isoproturon 50 WP while minimum value was observed for Aim 40 DF . These results are in line with who reported that herbicides application effectively controlled weeds.
These findings are also in conformity with those of , who reported that herbicides significantly reduced weed density. Similarly,stated that Puma Super 75 EW @ 1.25 L·ha–1 gave maximum control of narrow-leaved weeds in wheat out of varying herbicides applied at different doses. The best performance of Isoproturon 50 WP and other herbicidal applications could be attributed to the best control of weeds due to minimal weed competition which caused an increased flow of nutrients towards the grain and ultimately yield was increased. These results are supported by . They reported that herbicidal treatments significantly increased the grain yield in wheat. The maximum number of tillers m–2 was noted for Isoproturon 50 WP whereas minimum number was reported in weedy check. These results showed that maximum weed control enhanced the production of fertile tillers m–2 which subsequently contributed towards the increase in wheat yield. These results are in agreement with the work of who obtained an increase in tillering with the application of different herbicides. The low yield in weedy check plots indicated that weeds utilize maximum resources of the main crop which ultimately reduced the crop yield. These results are in conformation with those of , who applied Puma Super 75 EW and Topik 15 WP at different doses to control Avena fatua in wheat crop and reported that lesser dose of Topik 15 WP and higher dose of Puma Super 75 EW was required to control this weed. Wheat is the most important cereal crop in the USA, where it was planted on 23 million ha in 2012 .
Most of the wheat grown in the USA is winter wheat . Kansas state ranks first in winter wheat cultivation in the USA . Winter wheat is not a good competitor with some broadleaf weeds even when wheat emerges before weeds . Common weeds found in winter wheat in the US are blue mustard , cannabis grow tray henbit , flixweed , bushy wallflower , field pennycress , wild buckwheat , shepherd’s purse , and pinnate tansymustard.Their interference can cause significant yield reduction in winter wheat. Season-long competition of 11, 33, and 98 blue mustard plants·m−2 reduced wheat grain yields by 28%, 42%, and 51%, respectively . Conley and Bradley reported yield reductions of 13 and 38% because of henbit interference at 82 and 155 plants·m−2 , respectively. Northam et al. also reported wheat grain yield loss of 48% with 221 henbit plants·m−2 . Bushy wallflower at 272 plants·m−2 reduced wheat yields by 25% . Hence, winter annual broadleaf weed control is very important for successful wheat production. For more than two decades acetolactate synthase -inhibiting herbicides have been primary herbicides used in winter wheat, however continuous usage of those herbicides led to selection of ALS-inhibitor resistant weeds. Currently 126 ALS-inhibitor resistant weed species have been reported worldwide; 45 in the USA . Bushy wallflower and flixweed, two common broadleaf weeds in winter wheat, were reported ALS-inhibitor resistant in 2005 and 2006, respectively in Kansas . Rotating herbicides with different modes of action can avoid selection for weeds biotypes that are resistant to certain herbicides. Hence, there is a need for herbicides with alternative modes of action to ALS-inhibitor herbicides in wheat.Pyrasulfotole inhibits 4-hydoxyphenylpyruvate dioxygenase and blocks the pathway of prenylquinone biosynthesis in plants .