Absorption, fate, and soil activity of quinclorac in field bindweed (Convolvulus arvensis)

Laboratory and greenhouse experiments were conducted to examine the absorpt ion and fate of quinclorac in held bindweed and to assess the importance of quinclorac soil activity for field bindweed control. No foliar absorption of C-14-quinclorac occurred when applied alone, but absorption increased to 24% when quinclorac was applied with 2,4-D, 28% urea ammonium nitrate (UAN ), and methylated seed oil (MSO). Quinclorac translocation in field bindwee d was limited, as <18% of the total amount of absorbed radiolabeled materia l translocated out of the treated leaves 168 hours after treatment (HAT). Q uinclorac metabolism in the treated leaves was minimal; 95% of the recovere d C-14 was intact herbicide 168 HAT. Quinclorac soil activity on field bind weed was demonstrated in preemergence and soil subsurface applications. Pre emergence application of 35, 70, 140, or 280 g ha(-1) quinclorac reduced fi eld bindweed shoot growth. Field bindweed shoots exhibited auxinic herbicid e symptoms at all quinclorac rates. Subsurface layering of quinclorac below the root system at rates of 35 and 280 g ha(-1) also reduced shoot and roo t growth. Both herbicide rates induced malformation in root structure with a proliferation of lateral branching, swollen and fused root tips, and malf ormed root buds. Shoot growth from surviving roots replanted in untreated m edia was also reduced in both herbicide treatments. These findings suggest quinclorac soil activity may be important for field bindweed control.