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Title: Onion weed control with post-directed applications of pelargonic acid

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

Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2012
Publication Date: 5/1/2012
Citation: Webber III, C.L., Shrefler, J.W., Brandenberger, L.P. 2012. Onion weed control with post-directed applications of pelargonic acid [abstract]. Proceedings of Southern Weed Science Society, January 23-25, 2012, Charleston, South Carolina. Poster #35.

Interpretive Summary:

Technical Abstract: Organic onion 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 5 weed control treatments (1 herbicide applied at 3 rates) with sequential applications separated by 8 days, plus an untreated weedy-check and an untreated weed-free check) with 6 replications. The herbicide, Scythe (registered trademark) (57% pelargonic acid), was applied at 3, 6, and 9% v/v at 40 gpa. Intermediate day, sweet onion, cv. 'Candy,' were transplanted on April 5, 2010 into 2 rows per 6 ft-wide raised beds. Each plot consisted of two onion rows per 10 ft length of bed. Weed control (total, evening primrose, smooth crabgrass, and yellow nutsedge) increased as the rate of Scythe increased from 3 to 9% v/v. Initial, 1 day after initial treatment (DAIT), control for the total, evening primrose, and smooth crabgrass ratings were similar, but the smooth crabgrass control quickly declined after 1 DAIT. Injury increased as the rate of Scythe increased with a spike in injury following sequential application at 8 DAIT. All Scythe treatments produced significantly less marketable onions and weight/acre. Although onion injury was reduced compared to previous research with the over-the-top broadcast applications of potential organic herbicides, onion yields in this study were unacceptable due to the lack of weed control and crop injury. Further research should combine the use of corn gluten meal or mustard meal as preemergence herbicides combined with between row applications of post-emergence organic herbicides.