Sometimes environmental variables make herbicide application in recommended times unfeasible. Therefore, the evaluation of the herbicide application in a framework out of recommended schedules seems necessary. To do this, an experiment based on field conditions was performed by applying different doses of tribenuron-methyl herbicide on weeds Cleavers (Galium aparin) in winter wheat farmat the middle of itsstem elongation stage in the growing season 2013-2014. The experiment was conducted in a completely randomized block design (RCBD) with 3 replications including3 doses of tribenuron-methyl herbicide 10g/ha, 15g/ha, 20g/ha, an unweeded level and a hand weeded one. Results indicated that increasing the dose of herbicide would lead to a decline in the weed’s dry weight and its height -the highest level of decline was observed in 20g/ha dose. Maximum height of winter wheat was recorded for hand weeded level followed by 20g/halevel. Neither were grain yield nor yield components such as number of grains per spike, number of fertile spikelets per spike and thousand grain weight affected by these treatments. Based on this study, delay in applying this herbicide, despite reducing the weed biomass, left no impact on grain yield. Thus, the application of tribenuron-methyl herbicide at the middle of stem elongation stage of winter wheat is not recommended.
