Field studies assessed weed control and potato injury with rimsulfuron applied postemergence at various rates in combination with various adjuvants. Weed control was influenced by choice of adjuvant and rimsulfuron rate. Rimsulfuron at 0, 9, 18, 26, and 35 g ai/ha was applied with nonionic surfactant (NIS), crop oil concentrate (COC), methylated seed oil (MSO), or silicone-polyether copolymer (SIL). Potato injury was less than 5% for all rimsulfuron rates and adjuvant combinations. Redroot pigweed was controlled greater than or equal to 93% by all treatments except rimsulfuron at 9 g/ha SIL. Except for redroot pigweed, rimsulfuron treatments with SIL controlled kochia, hairy nightshade, common lambsquarters, and volunteer oats less than with other adjuvants. At lower rimsulfuron rates, weed control with rimsulfuron MSO tended to be greater than with rimsulfuron NIS or rimsulfuron COC. Common lambsquarters control was 75% or less regardless of rimsulfuron rate or adjuvant. Tuber yield generally increased with increasing rimsulfuron rates. Depending on rimsulfuron rate, tuber yield was 10 to 15% lower with rimsulfuron NIS or rimsulfuron COC compared to rimsulfuron MSO, while tuber yield was 18 to 37% lower with rimsulfuron SIL compared to rimsulfuron NIS, rimsulfuron COC, or rimsulfuron MSO.
Nomenclature: Rimsulfuron; common lambsquarters, Chenopodium album L. #3 CHEAL; hairy nightshade, Solanum sarrachoides # SOLSA; kochia, Kochia scoparia L. Shrad. # KCHSC; potato, Solanum tuberosum L. ‘Russet Burbank’; redroot pigweed, Amaranthus retroflexus L. # AMARE; volunteer oat, Avena sativa L. # AVESA.
Additional index words: Crop oil concentrate, methylated seed oil, nonionic surfactant, organosilicone.
Abbreviations: COC, crop oil concentrate; MSO, methylated seed oil; NIS, nonionic surfactant; PNW, Pacific Northwest; POST, postemergence; PRE, preemergence; SIL, silicone-polyether copolymer; WAT, weeks after treatment.
