THE EFFECT OF PIPERONYL BUTOXIDE AND ADJUVANTS ON SULFONYLUREA HERBICIDE ACTIVITY

Greenhouse studies showed that the mixed function oxidase inhibitor, p iperonyl butoxide (PBO), tank-mixed with the sulfonylurea herbicides, nicosulfuron, primisulfuron, and thifensulfuron, in the absence of eff ective adjuvants enhanced herbicide activity on both broadleaf and gra ss weed species. Effective adjuvants for nicosulfuron were K-3000 for common lambsquarters, Sylgard(R) 309 Surfactant for velvetleaf, K-2000 for barnyardgrass, and K-2000, K-3000, and Scoil(R) methylated seed o il for giant foxtail control, K-3000 and Sylgard 309 enhanced velvetle af control with primisulfuron and thifensulfuron. The 28% urea and amm onium nitrate (UAN) was more effective as an adjuvant with thifensulfu ron for velvetleaf than for common lambsquarters control. The enhancem ent of sulfonylurea herbicide activity with PBO was most apparent when other adjuvants were least effective.