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Punjab Agricultural University, Ludhiana, Punjab 141004, India
Germination, Herbicide, Seed heteromorphism, Weed control efficiency
Medicago denticulata Willd. is a winter annual weed infesting wheat. The present study was aimed to evaluate the effect of weed growth stage at the time of herbicide application (2,4-D, carfentrazone-ethyl and pre-mix herbicide metsulfuron-methyl plus sulfosulfuron) on efficacy of different post-emergence herbicides and herbicide carryover effects onto future generations. Herbicide sprays done at four-leaf stage of M. denticulata provided effective control whereas delayed application resulted in poor control with no visual injury. Significant increase in weed density was observed as the herbicides were sprayed at advanced growth stages of M. denticulata. Delayed application of all the herbicides at eight and twelve-leaf stage caused decrease in weed control efficiency than herbicide sprays done at four-leaf stage. However, application of herbicides at eight and twelve-leaf stages caused significant reduction in seed production potential of M. denticulata as compared to herbicide sprays done at four-leaf stage. Carfentrazone-ethyl had more pronounced effect on seed production potential of M. denticulata than 2,4-D. Whereas, metsulfuron-methyl plus sulfosulfuron was least effective in reducing fruit and seed number of M. denticulata. Seeds produced by M. denticulata plants after herbicide exposure were viable but dormant and exhibited decreased germination.