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Title: Post-directed application of a potential organic herbicide for bell peppers

Author
item Webber Iii, Charles
item SHREFLER, JAMES - Oklahoma Agriculture Experiment Station
item BRAMDEMBERGER, LYNN - Oklahoma State University

Submitted to: Annual Weed Control Research Reports
Publication Type: Experiment Station
Publication Acceptance Date: 3/1/2011
Publication Date: 4/21/2011
Citation: Webber III, C.L., Shrefler, J.W., Bramdemberger, L.P. 2011. Post-directed application of a potential organic herbicide for bell peppers. Oklahoma State University, Division of Agricultural Sciences and Natural Resources, Department of Horticulture and Landscape Architecture. Stillwater, Oklahoma. MP-162 p. 24-28.

Interpretive Summary: Organic pepper (Capsicum annuum L.) producers need appropriate herbicides that can effectively provide post-emergent weed control. Postemergent sequential applications of contact herbicides in organic crops may increase season-long control of weeds in bell peppers to offset the lack of systematic organic herbicides. Research was conducted in southeast Oklahoma (Atoka County, Lane, OK) to determine the impact of a potential organic herbicide on weed control efficacy, crop injury, and yields. The experiment included Scythe (registered trademark) (57% pelargonic acid) applied post-directed at 3, 6, and 9% v/v application rates, plus an untreated weedy-check and an untreated weed-free check with 4 replications. Bell pepper, cv. ‘Jupiter,’ was transplanted on May 28, 2010 in 1 row in 91-cm wide raised beds. The primary weeds included smooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.], cutleaf groundcherry (Physalis angulata L.), and spiny amaranth (Amaranthus spinosus L.). Scythe was post-directed applied on June 16 and then reapplied 8 days later (June 25). Smooth crabgrass (55.6%) and cutleaf groundcherry (66.3%) control peaked at 1 day after initial treatment (DAIT) with the 9% application rate. Scythe at 9% v/v rate also resulted in the greatest crop injury at 1 DAT (13.75%). The sequential application of Scythe did not significantly increase grass or broadleaf control. Although weed control and crop yields increased as application rates increased, the less than satisfactory weed control produced significantly lower pepper yields that the weed-free treatment.

Technical Abstract: Organic pepper (Capsicum annuum L.) producers need appropriate herbicides that can effectively provide post-emergent weed control. Research was conducted in southeast Oklahoma (Atoka County, Lane, OK) to determine the impact of a potential organic herbicide on weed control efficacy, crop injury, and yields. The experiment included Scythe (registered trademark) (57% pelargonic acid) applied post-directed at 3, 6, and 9% v/v application rates, plus an untreated weedy-check and an untreated weed-free check with 4 replications. Bell pepper, cv. ‘Jupiter,’ was transplanted on May 28, 2010 in 1 row in 91-cm wide raised beds. The primary weeds included smooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.], cutleaf groundcherry (Physalis angulata L.), and spiny amaranth (Amaranthus spinosus L.). Scythe was post-directed applied on June 16 and then reapplied 8 days later (June 25). Smooth crabgrass (55.6%) and cutleaf groundcherry (66.3%) control peaked at 1 day after initial treatment (DAIT) with the 9% application rate. Scythe at 9% v/v rate also resulted in the greatest crop injury at 1 DAT (13.75%). The sequential application of Scythe did not significantly increase grass or broadleaf control. Although weed control and crop yields increased as application rates increased, the less than satisfactory weed control produced significantly lower pepper yields that the weed-free treatment.