Environmental effects on CGA-248757 and flumiclorac efficacy/soybean tolerance

The effect temperature, light intensity, time to initial light exposure, relative humidity, and the presence of dew have on CGA-248757 and flumiclorac efficacy was evaluated in laboratory trials. Increasing temperature from 10 to 40 C increased CGA-248757 and flumiclorac activity on common lambsquarters by 79 and 87%, respectively. Similarly, increasing temperature from 10 to 40 C increased CGA-248757 and flumiclorac activity on redroot pigweed by 68 and 60%, respectively. Increasing light intensity from 0 to 1,000 μmol m−2 s−1 increased CGA-248757 activity on common lambsquarters and redroot pigweed by 92 and 93%, while flumiclorac activity increased 91 and 99%. Time to initial light exposure and relative humidity did not affect CGA-248757 or flumiclorac activity on common lambsquarters and redroot pigweed. The presence of dew reduced herbicidal activity of both compounds on common lambsquarters by 5% and redroot pigweed control with CGA-248757 and flumiclorac by 21 and 20%, respectively. Field applications of CGA-248757 or flumiclorac at 6:00 A.M., 2:00 P.M., and 10:00 P.M. indicate environmental conditions at application strongly influence soybean tolerance and weed control with CGA-248757 and flumiclorac. The greatest soybean injury occurred from CGA-248757 or flumiclorac applications at 6:00 A.M. compared with applications at 2:00 P.M. or 10:00 P.M. Common lambsquarters control was greatest when CGA-248757 or flumiclorac was applied at 6:00 A.M. or 2:00 P.M. compared with 10:00 P.M. However, redroot pigweed control was greatest when CGA-248757 or flumiclorac was applied at 2:00 P.M. Application time of day did not affect velvetleaf control with either herbicide.