BASIS FOR INTERACTIONS OF ETHOFUMESATE AND DESMEDIPHAM ON SUGARBEETS AND WEEDS

A synergistic interaction occurred when sugar beets (Beta vulgaris L. ''Mono-Hy Al'') were treated with mixtures of ethofumesate (2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulphonate) and desmedipham [ethyl m-hydroxycarbanilate carbanilate (ester)]. Depending on the stage of weed growth synergistic interactions were also observed on 2 weed species: wild mustard [Brassica kaber (DC.) L.C. Wheeler ''pinnatifida'' (Stokes) L.C. Wheeler] and wild oat (Avena fatua L.). Desmedipham penetrated the foliage more slowly than did ethofumesate. The rate of desmedipham penetration was positively correlated with the concentration of its formulants (solvents and adjuvants) in the spraying emulsion, and to a lesser extent with the formulants of ethofumesate. Increasing the spray volume also increased desmedipham penetration. None of these factors affected penetration by ethofumesate. 14C-labeled ethofumesate and desmedipham did not translocate out of treated leaves regardless of the concentration of formulants or active ingredients. The synergistic interaction is probably mainly due to the increased penetration by desmedipham when applied with ethofumesate.