Influence of Environmental Factors and Adjuvants on the Foliar Penetration of Acifluorfen in Velvetleaf (Abutilon theophrasti): An Analysis Using the Fractional Factorial Design

Two-level fractional factorial design experiments were conducted in growth chambers to determine the influence of environmental factors and adjuvants on the foliar penetration of the sodium salt of acifluorfen in velvetleaf. Relative humidity (RH) was found to have the greatest effect on penetration. Temperature was the second most important factor. Although soil moisture significantly affected penetration, this effect was much less than that produced by RH and temperature. Diammonium phosphate (DAP) was the most effective adjuvant tested. The use of DAP at 1.12 kg/ha significantly increased penetration. The effect of DAP was less than either RH or temperature. Oxysorbic (5 POE) surfactant also significantly increased penetration. Glycerol and oxtoxynol (7 to 8 POE) surfactant had no effect on penetration. In separate experiments, acifluorfen penetration at low and high RH and with the addition of DAP was measured to verify these results. Acifluorfen penetration into velvetleaf increased approximately ninefold with changes in RH from low to high. Penetration increased sevenfold when DAP was added. DAP was by far the most effective adjuvant increasing acifluorfen penetration into velvetleaf under conditions of low RH. Oxysorbic (5 POE) surfactant slightly increased penetration under these conditions.