ABSTRACT

Experiments were conducted at three locations in Alberta to evaluate the effect of photodegradation ofsethoxydim{2-[l-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-l-one}. The degrading effect of ultraviolet radiation (UV, 300 to 400 nm) was investigated under field conditions as measured by the phytotoxic activity of sethoxydim on preselected samples of volunteer barley (Hordeum vulgare L.). Physical screening treatments were employed to control the spectral quality of radiant energy impinging on sethoxydim-treated plants. Several spray adjuvants (oil concentrate, ammonium sulfate, BAS 815, BAS 890) were also examined in mixtures with sethoxydim to determine their influence on sethoxydim activity on barley. Visible light (400 to 700 nm) had little or no influence on sethoxydim activity. However, exposure to UV radiation often dramatically reduced the activity of sethoxydim. The inclusion of adjuvants in the spray mixture counteracted some of the deleterious effects of UV radiation. Of the adjuvants tested, BAS 815 or BAS 890 most effectively preserved sethoxydim activity in the presence of UV radiation.