FLUAZIFOP-P REDUCES STRAWBERRY (FRAGARIA X ANANASSA) TOLERANCE TO TERBACIL

Greenhouse and field experiments were conducted to characterize a syne rgistic interaction between fluazifop-P and terbacil in strawberry (Fr agaria x ananassa Duchesne). In the greenhouse, injury from foliar ter bacil applications generally increased two- or more fold when 75 or 15 0 g/ha fluazifop-P was applied foliarly 24 h later to either a terbaci l tolerant ('Veestar') or sensitive ('Kent') strawberry cultivar. Syne rgism also occurred when terbacil was applied as a soil drench and flu azifop-P was applied 5 d later. There was little difference in effect between tank-mixed and sequential applications made 0.5 and 20 min apa rt. Increased injury was also observed with intervals up to 6 d betwee n applications in the greenhouse, and the order of herbicide applicati on did not affect injury level. Similar results were obtained in field experiments on newly planted 'Honeoye' and 'Cavendish' strawberry. An interval of 6 d or more between terbacil and fluazifop-P application is suggested to minimize the risk of increased crop injury.