ARS | Publication request: Post-directed application of pelargonic acid for squash

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: January 24, 2011
Publication Date: August 31, 2011
Citation: Webber III, C.L., Shrefler, J.W., Brandenberger, L.P. 2011. Post-directed application of pelargonic acid for squash [abstract]. Weed Science Society of America Meeting, February 7-10, 2011, Portland, Oregon. Available: http://wssaabstracts.com/public/4/proceedings.html.

Technical Abstract: Organic squash (Cucurbita pepo 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. Yellow squash, cv. 'Enterprise,' was direct-seeded 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 level at 7 days after the initial spray treatment (DAT). Smooth crabgrass (98%), cutleaf groundcherry (94%), and spiny amaranth control (94%) control peaked at 9 DAT (1 day after the sequential treatment) with the 9% application rate. Scythe at 9% also resulted in the greatest crop injury at 9 DAT (12.5%). The sequential application of Scythe significantly increased grass or broadleaf control at all application rates. The 6 and 9% Scythe treatments produced equivalent squash yields (squash/ha and kg/ha) as the weed-free treatment and greater yields than the weedy check.