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

Laboratory and greenhouse experiments were conducted to examine the absorption and fate of quinclorac in field bindweed and to assess the importance of quinclorac soil activity for field bindweed control. No foliar absorption of 14C-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 bindweed was limited, as < 18% of the total amount of absorbed radiolabeled material translocated out of the treated leaves 168 hours after treatment (HAT). Quinclorac metabolism in the treated leaves was minimal; 95% of the recovered 14 C was intact herbicide 168 HAT. Quinclorac soil activity on field bindweed was demonstrated in preemergence and soil subsurface applications. Preemergence application of 35, 70, 140, or 280 g ha−-1 quinclorac reduced field bindweed shoot growth. Field bindweed shoots exhibited auxinic herbicide 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 root growth. Both herbicide rates induced malformation in root structure with a proliferation of lateral branching, swollen and fused root tips, and malformed root buds. Shoot growth from surviving roots replanted in untreated media was also reduced in both herbicide treatments. These findings suggest quinclorac soil activity may be important for field bindweed control.