Physiological basis for CGA-248757 and flumiclorac selectivity in five plant species

Greenhouse and laboratory studies were conducted to determine the physiolog ical basis for CGA-248757 and flumiclorac selectivity in five plant species . CGA-248757 and flumiclorac selectively control weeds postemergence (POST) by inhibiting protoporphyrinogen oxidase (Protox). Injury symptoms from CG A-248757 and flumiclorac include rapid desiccation and necrosis similar to injury from diphenyl ether and bipyridinium herbicides. Species sensitivity to CGA-248757 and flumiclorac was evaluated by comparing the dry weight re duction from POST applications. Abutilon theophrasti was sensitive to both herbicides, Amaranthus retroflexus was more sensitive to flumiclorac than C GA-248757, Brassica kaber was sensitive to CGA-248757 bur tolerant of flumi clorac, and Zea mays and Glycine max were tolerant of both herbicides. Stud ies evaluated CGA-248757 and flumiclorac retention, absorption, translocati on, and metabolism. Enhanced herbicide metabolism contributed to the tolera nce of A. retroflexus to CGA-248757 and B. kaber to flumiclorac. Decreased herbicide retention, absorption, and translocation coupled with increased m etabolism contributed to Z. mays tolerance of CGA-248757 and flumiclorac. D ecreased herbicide retention and increased herbicide metabolism provided G. max tolerance of both herbicides.