Agrichemical interactions with propanil on propanil-resistant barnyardgrass (Echinochloa crus-galli)

Agrichemical interactions between propanil; the herbicides HOE 30374, pendi methalin, piperophos, quinclorac, and thiobencarb; and the insecticide carb aryl were evaluated under field conditions to find synergistic or additive interactions useful to control a barnyardgrass biotype resistant to propani l (R-BYG) without injuring rice. Propanil and each compound were evaluated at four rates for a total of 16 rate combinations for each additive. Averag ed over all experiments, 2- to 3-leaf R-BYG control with propanil alone at 0.83, 1.65, 3.3, and 6.6 kg ai/ha was 33, 53, 62, and 81% at 7 d after trea tment (DAT). Propanil-susceptible barnyardgrass (S-BYG) response to propani l alone at similar rates was 52, 73, 88, and 94% control. HOE 30374, carbar yl, piperophos, or pendimethalin in combination with propanil produced syne rgistic effects on R-BYG. For each compound tested, at least one rate combi nation with propanil controlled R-BYG > 80% with minimal rice injury (< 20% ) at 7 DAT. Use of these combinations of compounds could provide more effec tive control of this resistant biotype and help prevent its spread.