Response of Bermudagrass (Cynodon dactylon) to Siduron

The efficacy of siduron [1-(2-methylcyclohexyl)-3-phenylurea] on bermudagrass [Cynodon dactylon (L.) Pers. CYNDA3] in bentgrass (Agrostis spp.) golf greens was evaluated. In field trials, the frequency of bermudagrass occurrence in most treatments either remained unchanged or increased. Cultural treatments such as vertical mowing and aerifying did not improve the efficacy. Dry-weight measurements showed no significant differences due to chemical treatments. In pot trials, differential susceptibility of collections of bermudagrass was evident, supporting the hypothesis that selection of tolerant strains over several years' use of the herbicide has caused the poor efficacy seen in the field. Differences in the development of shoot, root, and rhizome systems between treated and untreated were evident.