Quackgrass (Agropyron repens) Biotype Response to Sethoxydim and Haloxyfop

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Abstract
Crown bud, tiller, and rhizome development was studied in 10 quackgrass biotypes at two stages (three-to four- and seven- to eight-leaf stages) of development to determine if differential development of these structures influenced control with sethoxydim and haloxyfop. There was a differential response among the 10 biotypes to both sethoxydim and haloxyfop at both stages of development. The biotypes differed in the number of crown buds, tillers, and rhizomes that formed at both stages of development. In the three- to four-leaf stage, the biotypes with the greatest number of crown buds were the most difficult to control. These results suggest that in the susceptible stage (three-to four-leaf) the quackgrass biotypes with the least number of crown buds will be the easiest to control; however, by the time all the biotypes reach the seven- to eight-leaf stage even the biotypes with the lowest number of crown buds have enough crown buds that they become difficult to control with either sethoxydim or haloxyfop.