Sulfentrazone was applied POST at 13, 26, or 53 g ai/ha alone or in combination with metribuzin at 280 or 420 g ai/ha in field trials conducted with ‘Russet Burbank’ potatoes in 2002 to 2004. Sulfentrazone alone provided less than 84% redroot pigweed, common lambsquarters, and kochia control, although control usually improved to 90% or greater when metribuzin was included. Hairy nightshade control reached 90% only when the highest rates of both herbicides were applied in combination. Sulfentrazone alone did not provide any volunteer oat control, whereas control was 85% when the highest metribuzin rate was included. Potato crop injury, consisting of chlorosis, interveinal blackening of the leaves, eventual necrosis, leaf malformation, and plant stunting, increased as the sulfentrazone rate increased. In contrast, injury decreased as metribuzin rate increased from 0 to 420 g/ha, when averaged across sulfentrazone rates. Reduction in injury levels and increased weed control translated to improved tuber yields as metribuzin rate increased. However, when sulfentrazone was combined with the highest metribuzin rate, potato injury was still relatively high at 26 and 18% at 1 and 4 wk after treatment, and acceptance of sulfentrazone applied POST with metribuzin by potato growers is unlikely.
Nomenclature: Metribuzin, sulfentrazone, common lambsquarters, Chenopodium album L. #3 CHEAL, kochia, Kochia scoparia (L.) Shrad. # KCHSC, redroot pigweed, Amaranthus retroflexus L. # AMARE, hairy nightshade, Solanum sarrachoides Sendtn # SOLSA, volunteer oat, Avena sativa L. # AVESA, potato, Solanum tuberosum L. ‘Russet Burbank’.
Additional index words: Herbicide interaction, potato crop response, safening effect.
Abbreviations: WAT, weeks after treatment.