Uptake, translocation and metabolism of fluazifop‐butyl in Setaria viridis

SUMMARY The uptake and translocation of fluazifop‐butyl was investigated in Setaria viridis. Young plants (three to four leaves) with a portion of the second, third or fourth leaf covered, were sprayed with a dose equivalent to 0.25 kg a.i. ha‐1. 14C‐fluazifop‐butyl was subsequently applied to the unsprayed area and the treatment resulted in plant death within 2 wk. Uptake by leaf 3 was rapid, with less than 5% of the applied dose remaining on the leaf surface after 24 h. The highest proportion of 14C‐activity was retained in the treated portion of the leaf. Only 2% of the applied dose was translocated from leaf 3 and 0. 76% accumulated in the apical meristem. Uptake by the younger leaf 4 was more rapid and the pattern of translocation differed in that more 14‐‐activity accumulated in apical meristematic tissue. 6–30% of the applied dose was undetected and this was greatest when foliar uptake was slow. Artificial leaf surface experiments indicated that this undetected activity may have been due to volatility of fluazifop‐butyl or degradation to volatile products. 14C‐activity extracted from treated leaves was identified as fluazifop‐butyl, fluazifop acid and polar conjugates. The major 14C‐activity extracted from the apical meristem was fluazifop acid and no fluazifop‐butyl was detected in this extract.