ZOYSIAGRASS TOLERANCE TO SELECTIVE HERBICIDES FOR THE REMOVAL OF BERMUDAGRASS AND THE DISTRIBUTION OF THE ANNUAL BLUEGRASS WEEVIL (LISTRONOTUS MACULICOLLIS) IN KENTUCKY

Bermudagrass (Cynodon dactylon) may be a problematic weed within zoysiagrass (Zoysia spp.) swards across its entire range. The objective of this study was to determine the efficacy of the herbicide safener metcamifen + trifloxysulfuron-sodium, in conjunction with fluazifop-P-butyl, at removing bermudagrass from zoysiagrass and how varying levels of treatment affected bermudagrass control and zoysiagrass tolerance. Field studies tested rates of metcamifen + trifloxysulfuron-sodium applied with fluazifop-P-butyl compared to treatments of fluazifop alone and fenoxaprop with triclopyr. All treatments controlled bermudagrass, and treatments with the herbicide safener remained under the 20% injury threshold for zoysiagrass for ≤ to 15 days compared to ≥ 46 days across the study for the remaining treatments. This is the first report of complete suppression of bermudagrass without unacceptable injury to zoysiagrass. Listronotus maculicollis is an economically important pest of turfgrass that has historically been confined to the Northeastern USA. In recent years, this pest has been found causing damage to golf courses outside of its traditional range. In Kentucky, damage from L. maculicollis was first reported in 2018. Although the presence of the weevil has been confirmed, little was known about the distribution and abundance of L. maculicollis within the state. The objective of this study was to conduct a statewide survey of golf courses superintendents in Kentucky and develop a map of the known distribution of L. maculicollis in the state. The results of the survey showed that the current distribution of L. maculicollis is limited to the physiographic Bluegrass region of the state which contains the most populous cities and the highest number of golf courses.