Weed management in wheat fields

In order to investigate some of weed management problems of wheat fields, a research project was carried out during 2003 to 2009 wawith 19 sub-projects in most wheat growing locations of Iran. Subjects included weed loss assessment, weed distribution mapping using Geographical Information System (GIS), biology and ecophysiology of some noxious weeds of wheat, introducing some new herbicides for optimize chemical weed control, investigating reasons to resistance of weeds to current herbicides and introducing appropriate management solution, investigating residues of herbicides used in wheat and their negative effects in rotation, study on sprayers used in wheat and their problems during application, noxious weed control in wheat, increasing efficacy of herbicides using tank-mixture and adjuvants, finally, study on wheat seed contamination of weedsand the possibility of weed seed distribution via wheat seed. This study presented map, frequency, and abundance of weeds in wheat fields for different locations and weed species. Results showed that the average of weed damage in wheat fields is 23.36 percent. Results of weed resistance to herbicides indicated that some biotypes of wild oat (Avena ludoviciana), canary grass (Phalaris minor) and rye grass (Lolium rigidum) in some locations such as Kermanshah, Kuzestan, Fars, etc., are resistant to some Aryloxyphenoxy propionate herbicides and herbicides like Atlantis, Total, Apryros, and Chevalier were introduced to control these biotypes. Results of residues of these herbicides on rotation crops of wheat indicated that Megaton and Total had negative effects on mung bean, but in Khuzestan and Fars, these herbicides had no negative effect on corn yield. Negative effect of Total, chevalier and Atlantis in Kermanshah, and Atlantis in Golestan was observed on corn yield. The three mentioned herbicides had negative effects on chickpea and sunflower. Canola grain yield was reduced by application of Chevalier and Atlantis in wheat fields which was in rotation. Additionally, the herbicide "Axial" was registered for herbicide resistant management in wheat. Wild barley species in wheat were controlled by application of Total and Apyros at 4th leaves stage of mentioned weeds. Study on the biology of weeds determined some criteria which could be used for their management in wheat fields. The results also showed that 17% of farmers use inappropriate sprayers for chemical weed control in wheat, and have little knowledge of sprayer on calibration, nozzle type and safety. Regarding contamination of certified wheat seeds, many seed cleaners had problem for cleaning some noxious weed seeds.