Propanil Selectivity for Green Foxtail (Setaria viridis) in Wheat (Triticum aestivum)

Retention, absorption, translocation, and metabolism of propanil (3′,4′-dichloropropionanilide) in tolerant wheat ( Triticum aestivum L. ‘Era’) and susceptible green foxtail [ Setaria viridis (L.) Beauv. ♯ 3 SETVI] were studied to determine the basis of selectivity. Green foxtail retained 7.7 times more spray on a mg/g fresh weight basis than did wheat. Absorption of 14 C-propanil by green foxtail was greater than by wheat during most of the 48-h uptake period, but differences in absorption were not large enough for absorption to be a major selectivity factor. Translocation of foliar-applied 14 C-propanil was limited in both species; after 48 h, 96.7% of absorbed 14 C remained in the treated wheat leaf and 99.7% remained in the treated green foxtail leaf. Limited metabolism of 14 C-propanil occurred in green foxtail, with only 6.4% of extractable 14 C-propanil metabolized to dichlorolactanilide and unknown 14 C-compounds during a 72-h period. Wheat metabolized 65.8% of the extractable 14 C-propanil to dichloroaniline and unknown 14 C compounds by 72 h after treatment. The results of this research indicate that spray retention and propanil metabolism are the major factors involved in wheat tolerance and green foxtail susceptibility to propanil.