Sensitivity of Ambrosia artemisiifolia to glufosinate and glyphosate at various developmental stages

P>Glufosinate and glyphosate at 375 g a.i. ha-1 and 540 g a.e. ha-1, respectively, were assessed for control of Ambrosia artemisiifolia under non-crop conditions at four different developmental stages (vegetative, BBCH 14; bud appearance, BBCH 53-55; onset of pollen production, BBCH 61; mid female flowering, BBCH 73-77). Both herbicides displayed high efficacies at all development stages. However, after treatments at BBCH 14, new emergence or re-growth of A. artemisiifolia led to the presence of plants that produced pollen and seeds. Treatments at BBCH 53-55 gave more than 99.9% reduced pollen production. Seed production was more than 99.9% reduced by glyphosate and 92.0-99.8% by glufosinate. Treatments at BBCH 61 suppressed viable seed production by more than 99.8%. When treatments were made at BBCH 73-77, seed production by A. artemisiifolia was not significantly affected, but seed viability was decreased by 10-85%. Although significantly reduced, the number of viable seeds was still 283-652 and 827-3893 m-2 in the plots treated by glufosinate and glyphosate respectively. It is concluded that on non-crop areas, herbicide treatment of A. artemisiifolia at bud appearance (BBCH 53-55) with glufosinate or glyphosate gave the most effective control of both pollen and seed production.