Annual Bluegrass Herbicide Resistance Caused by ALS Gene Mutation in Korea

Abstract

Acetolactate synthase (ALS)‐inhibiting herbicide is widely used for control of annual bluegrass (Poa annua L.) infestation in zoysiagrass (Zoysia spp.) fairways. Field experiments were conducted 2015 and 2016 to investigate ALS herbicide resistance of annual bluegrass at the Ansung Benest Golf Club in Korea, where application of trifloxysulfuron (0.008 g m−2) resulted in poor control for 2 yr. Control of annual bluegrass was significantly less (<34%) in flazasulfuron, foramsulfuron, and trifloxysulfuron treatments than in asulam treatment (83%). In dose‐response experiments, the resistant annual bluegrass survived (>80%) 40 d after treatment in flazasulfuron, foramsulfuron, and trifloxysulfuron treatments, which were applied 10 times at labeled rates. DNA sequencing results indicated that the resistance of annual bluegrass was associated with the tryptophan to leucine target‐site mutation at ALS codon position 574. These results confirm the risk of annual bluegrass herbicide resistance at golf courses in Korea and the need for new effective herbicides that may be useful in delaying or avoiding herbicide resistance.