A method of producing pollen that reduces fitness of at least one weed species of interest is provided. The method comprises treating the pollen of plants of a weed species of interest with an irradiation regimen selected from the group consisting of:(i) X-ray radiation at an irradiation dose of 10-1600 Gy；(ii) gamma radiation at an irradiation dose of 10-2000 Gy；(iii) particle radiation； and(iv) UV-C radiation at an irradiation dose of 100 μJ/cm2-50 J/cm2, with the proviso that when said weed is A. palmeri, when said irradiation is X-ray, the irradiation dose is not 300 Gy and wherein when said irradiation is gamma irradiation the irradiation dose is not 100, 300 and 500 Gy, and wherein when said radiation is UV-C the dose radiation is not 2 J/cm2.
