POSTEMERGENCE BROADLEAF WEED-CONTROL IN POTATO (SOLANUM-TUBEROSUM) WITH RIMSULFURON AND HOE-075032

Few postemergence (POST) herbicides provide adequate control of broadleaf weeds in potato. Field experiments were conducted at Lethbridge and Vauxhall, Alberta in 1991 and 1992 to determine the suitability of rimsulfuron and HOE-075032 for selective POST control of weeds in potato. Rimsulfuron applied at 15 to 30 g ai/ha controlled flixweed, kochia, and redroot pigweed and suppressed the growth of redstem filaree. HOE-075032 at 50 to 60 g ai/ha provided comparable control. The potato cultivars, 'Shepody,' 'Norchip,' 'Russet Burbank,' 'Niska,' and 'Ranger Russet,' tolerated up to 80 g/ha rimsulfuron, but rimsulfuron at 120 g/ha caused fissures in some tubers and reduced marketable and total tuber yields. Tuber quality factors such as specific gravity and chipping ability were not affected by rimsulfuron. HOE-075032 at 15 to 30 g/ha caused fissures in tubers and reduced marketable and total tuber yield of all potato cultivars. Rimsulfuron, but not HOE-075032, provided excellent selective POST broadleaf weed control in potato. Nomenclature: HOE-075032, 3-(4,6-dimethoxypyrimidin-2-yl)-1-(N-methyl-N-methylsulfonyl-aminosulfonyl)-urea; rimsulfuron, N-[[(4,6-dimethoxy-2-pyrimidinyl)amino] carbonyl]-3-(ethylsulfonyl)-2-pyridinesulfonamide; flixweed, Descurainia sophia L. Webb ex Prantl #(3) DESSO; kochia, Kochia scoparia (L.) Schrad. # KCHSC; redroot pigweed, Amaranthus retroflexus L. # AMARE; redstem filaree, Erodium cicutarium (L.) L'Her. ex Ait. # EROCI; potato, Solanum tuberosum L. 'Russet Burbank.'