Temperature, adjuvants, and UV light affect sethoxydim phytotoxicity

Experiments were conducted using oat in the greenhouse to determine phytoto xicity and spray deposit characteristics of sethoxydim on oat as influenced by adjuvants, ultraviolet (UV) light, and temperature at and shortly after application. Petroleum oil of low viscosity was equal or more effective wi th sethoxydim when applied at 10 than at 25 C, but high-viscosity petroleum oil was more effective at 25 than at 10 C. UV Light reduced sethoxydim eff icacy more for high-than low-viscosity petroleum oil adjuvant at 25 C, but not at 10 C. Commercial vegetable oil adjuvant was less effective with seth oxydim at 10 than at 25 C, and UV light reduced efficacy at both temperatur es. Commercial methylated vegetable oil was the most effective adjuvant and efficacy was only slightly reduced by UV light at 25 C. A secondary alcoho l surfactant that is considered hydrophilic enhanced sethoxydim efficacy ev en when exposed to UV light. Adjuvants that gave discernible uniform spray deposits with close contact to the epicuticular surface, including over ant iclinal walls, resulted in the most effective treatments. The results indic ated that temperature at application is important to adjuvant efficacy, par tly because of the effect on spray deposit characteristics.