Adjuvants Influenced Saflufenacil Efficacy on Fall-Emerging Weeds

Abstract Saflufenacil is a new herbicide being developed for preplant burndown and PRE broadleaf weed control in field crops, including corn, soybean, sorghum, and wheat. Field experiments were conducted in 2006 and 2007 at Concord, in northeast Nebraska, with the objective to describe dose–response curves of saflufenacil applied with several adjuvants for broadleaf weed control. Dose–response curves based on log-logistic model were used to determine the effective dose that provides 90% weed control (ED90) values for six broadleaf weeds (field bindweed, prickly lettuce, henbit, shepherd's-purse, dandelion, and field pennycress). Addition of adjuvants greatly improved efficacy of saflufenacil. For example, the ED90 values for field bindweed control at 28 d after treatment were 71, 20, 11, and 7 g/ha for saflufenacil applied alone, or with nonionic surfactant (NIS), crop oil concentrate (COC), or methylated seed oil (MSO), respectively. MSO was the adjuvant that provided the greatest enhancement of saflufenacil across all species tested. COC was the second-best adjuvant and provided control similar to MSO on many weed species. NIS provided the least enhancement of saflufenacil. These results are very similar to the proposed label dose of saflufenacil for burndown weed control, which will range from 25 to 100 g/ha with MSO or COC. We believe that such a dose would provide excellent burndown control of most broadleaf weed species that emerge in the fall in Nebraska. Nomenclature: Saflufenacil; dandelion, Taraxacum officinale Weber; field bindweed, Convolvulus arvensis L.; field pennycress, Thlaspi arvense L.; henbit, Lamium amplexicaule L.; prickly lettuce, Lactuca serriola L.; shepherd's-purse, Capsella bursa-pastoris (L.) Medik.; corn, Zea mays L.; sorghum, Sorghum bicolor (L.) Moench; soybean, Glycine max L.; wheat, Triticum aestivum L.

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