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Title: Impact of over-the-top broadcast applications of Racer® on onion weed control

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

Submitted to: Extension Publications
Publication Type: Experiment Station
Publication Acceptance Date: 1/1/2010
Publication Date: 1/8/2010
Citation: Webber III, C.L., Shrefler, J.W., Brandenberger, L.P. 2010. Impact of over-the-top broadcast applications of Racer® on onion weed control. 2009 Vegetable Trial Report. Oklshoma State University, Division of Agricultural Sciences and Natural Resources, Department of Horticulture and Landscape Architecture. Stillwater, OK. MP-162 p. 42-44.

Interpretive Summary: Weeds reduce crop yields, increase production costs, and can be hosts for crop diseases and detrimental insects. All components entering into the organic crop production system must be approved for organic use, including herbicides. Organic onion producers need organic herbicides that can effectively provide post-emergent weed control. Racer (registered trademark) is a potential herbicide for organically grown food crops. The main component (40%) of Racer is ammonium nonanoate (ammonium pelargonate), which occurs in nature and is primarily formed from biodegradation of higher fatty acids. Research was conducted in southeast Oklahoma (Atoka County, Lane, OK) to determine the effect of application rates and broadcast application of Racer on weed control efficacy, crop injury, and yields. Intermediate day, sweet onion cvs. 'Candy' and 'Cimarron' were transplanted on March 20, 2009 into 2 rows per 6 ft-wide raised beds. Each plot consisted of two onion rows per 10 ft length of bed. The experiment included 8 weed control treatments (3 application rates at 2 hand-weeding levels, plus an untreated weedy-check and an untreated weed-free) with 4 replications. Broadcast applications of Racer at 7.5 produced poor (70% or less) broadleaf weed control, while Racer at 10 and 15% provided excellent (equal to or greater than 90%) total broadleaf weed control through 10 DAT. Onion injury increased as Racer application rate increased with no significant difference among treatments at 18 DAT. Crop injury and lack of weed control from Racer did reduced crop yields compared to the untreated weedy-check. If the Racer's application method can be modified to reduce crop injury, the higher application rate has potential to make significant impact on broadleaf weed control in spring-transplanted onions.

Technical Abstract: The weed control challenges for onion production are formidable; however, these challenges are even greater for those considering organic crop production. Organic onion producers need organic herbicides that can effectively provide post-emergent weed control. Racer (registered trademark) is a potential herbicide for organically grown food crops. The main component (40%) of Racer is ammonium nonanoate (ammonium pelargonate), which occurs in nature and is primarily formed from biodegradation of higher fatty acids. Research was conducted in southeast Oklahoma (Atoka County, Lane, OK) to determine the effect of application rates and broadcast application of Racer on weed control efficacy, crop injury, and yields. Intermediate day, sweet onion cvs. 'Candy' and 'Cimarron' were transplanted on March 20, 2009 into 2 rows per 6 ft-wide raised beds. Each plot consisted of two onion rows per 10 ft length of bed. The experiment included 8 weed control treatments (3 application rates at 2 hand-weeding levels, plus an untreated weedy-check and an untreated weed-free) with 4 replications. Broadcast applications of Racer at 7.5 produced poor (70% or less) broadleaf weed control, while Racer at 10 and 15% provided excellent (equal to or greater than 90%) total broadleaf weed control through 10 DAT. Onion injury increased as Racer application rate increased with no significant difference among treatments at 18 DAT. Crop injury and lack of weed control from Racer did reduced crop yields compared to the untreated weedy-check. If the Racer’s application method can be modified to reduce crop injury, the higher application rate has potential to make significant impact on broadleaf weed control in spring-transplanted onions.