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Title: Post-directed weed control in squash

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

Submitted to: Proceedings of Horticultural Industry Show
Publication Type: Proceedings
Publication Acceptance Date: 12/15/2011
Publication Date: 5/6/2012
Citation: Webber III, C.L., Shrefler, J.W., Brandenberger, L.P. 2012. Post-directed weed control in squash. Proceedings of Horticultural Industry Show, January 6-7, 2012, Tulsa, Oklahoma. p. 156-169.

Interpretive Summary: Organic squash (Cucurbita pepo L.) producers need appropriate herbicides that can effectively provide season-long 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. Yellow squash, 'Enterprise,' was direct-seeded in a single row on June 21, 2010 into raised 91-cm centered 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 July 13 and then reapplied 8 days later (July 21). Grass weed control (78%) and broadleaf weed control (69%) with the 9% Scythe treatment were at their lowest levels at 7 days after the initial spray treatment (DAIT). Smooth crabgrass (98%), cutleaf groundcherry (94%), and spiny amaranth (94%) control peaked at 9 DAIT (1 day after the sequential treatment) with the 9% application rate. Scythe at 9% also resulted in the greatest crop injury at 9 DAIT (12.5%). The sequential application of Scythe significantly increased grass and broadleaf control at all application rates. The 6 and 9% Scythe treatments produced equivalent squash yields (squash/acre and lb/acre) as the weed-free treatment and greater yields than the weedy check. These results provide producers with information for optimizing weed control with pelargonic acid.

Technical Abstract: Organic squash (Cucurbita pepo L.) producers need appropriate herbicides that can effectively provide season- long 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. Yellow squash, 'Enterprise,' was direct-seeded in a single row on June 21, 2010 into raised 91-cm centered 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 July 13 and then reapplied 8 days later (July 21). Grass weed control (78%) and broadleaf weed control (69%) with the 9% Scythe treatment were at their lowest levels at 7 days after the initial spray treatment (DAIT). Smooth crabgrass (98%), cutleaf groundcherry (94%), and spiny amaranth (94%) control peaked at 9 DAIT (1 day after the sequential treatment) with the 9% application rate. Scythe at 9% also resulted in the greatest crop injury at 9 DAIT (12.5%). The sequential application of Scythe significantly increased grass and broadleaf control at all application rates. The 6 and 9% Scythe treatments produced equivalent squash yields (squash/acre and lb/acre) as the weed-free treatment and greater yields than the weedy check.