Postemergence effects of different distribution patterns of tri‐allate granules on Avena fatua L. and wheat plants

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Summary:The phytotoxicity of 10% w/w tri‐allate granules to emerged plants of Avena fatua L. and wheat was investigated in the glasshouse, and to A. fatua alone under outdoor conditions. Tri‐allate was applied at 1.68 and 3.36 kg a.i./ha using two patterns of granule distribution (1) the granules uniformly distributed over the soil surface and (2) the same weight of granules as in (1) but applied only to a central area of the soil surface. Wheat was very tolerant of high concentrations of tri‐allate. Under optimum conditions of temperature and soil moisture in the glasshouse phytotoxic effects on wild oats were visible within 6 h and coleoptile or primary leaf entrapment was observed within 3 to 4 days of treatment. Phytotoxic effects of tri‐allate were detectable at distances up to 12 cm from the site of restricted‐granule application, although beyond 8 cm the effect was sub‐lethal. On a sloping soil surface (1:8 gradient) the dispersal of tri‐allate was approximately the same upwards or downwards from the site of herbicide application. Under outside conditions where the mean temperature was about 5 C tri‐allate dispersal was sub‐lethal beyond 3 cm although it evidently occurred primarily as vapour.