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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #308457
Title: Pelargonic acid for weed control in organic Vidalia sweet onion production

Author
item Johnson, Wiley - Carroll
item DAVIS, JERRY - University Of Georgia

Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/2014
Publication Date: 12/1/2014
Citation: Johnson, W.C., Davis, J.W. 2014. Pelargonic acid for weed control in organic Vidalia sweet onion production. HortTechnology. 24(6):696-701.

Interpretive Summary: Weed management in organic Vidalia® sweet onion is heavily dependent on cultivation with a tiner weeder. If the initial cultivation is delayed, emerged weeds are not controlled by the tine weeder. In these cases, herbicides derived from natural products could be used to control the emerged weeds prior to the initial cultivation. Clove oil has been evaluated for this use, but cool-season weed control is inconsistent. Pelargonic acid is a herbicide that can be derived from natural sources. Field trials were conducted from 2011 through 2013 to determine the efficacy of pelargonic acid for cool-season weed control in organic Vidalia® sweet onion. All possible combinations of four herbicides and three cultivation regimes using a tine weeder were evaluated. Herbicides evaluated were pelargonic acid (3% and 5% by vol.), clove oil (10% by vol.) (in 2011 and 2012), d-limonene (14%) (2013 only), and a nontreated control. Cultivation regimes were twice (2X) and four times (4X) at biweekly intervals, and a non-cultivated control. Main effects of cultivation and herbicides were independent for all parameters, with no improvement when used in combination compared to either factor alone. Cultivation 2X and 4X controlled cool-season weeds and improved onion yields, which is consistent with previous research. Pelargonic acid (5%) controlled weeds similar to clove oil (2011 and 2012) and d-limonene (2013), with cool-season weed control efficacy being inconsistent among all herbicides. Onion yield response to weed control from any of the herbicides, including pelargonic acid, was also inconsistent. Pelargonic acid does not offer any weed control advantage over other herbicides derived from natural sources in organic onion production.

Technical Abstract: Cultivation using a tine weeder is a proven means to manage weeds in organic Vidalia® sweet onion production. If the initial cultivation is delayed, emerged weeds are not controlled by the tine weeder. In these cases, herbicides derived from natural products could be used to control the emerged weeds prior to the initial cultivation. Clove oil has been evaluated for this use, but cool-season weed control is inconsistent during the winter season when Vidalia® sweet onion are grown. Pelargonic acid is a herbicide that can be derived from natural sources. Field trials were conducted from 2011 through 2013 to determine the efficacy of pelargonic acid for cool-season weed control in organic Vidalia® sweet onion. All possible combinations of four herbicides and three cultivation regimes using a tine weeder were evaluated. Herbicides evaluated were pelargonic acid (3% and 5% by vol.), clove oil (10% by vol.) (in 2011 and 2012), d-limonene (14%) (2013 only), and a nontreated control. Cultivation regimes were twice (2X) and four times (4X) at biweekly intervals, and a non-cultivated control. Main effects of cultivation and herbicides were independent for all parameters, with no improvement when used in combination. Cultivation 2X and 4X controlled cool-season weeds and improved onion yields, which is consistent with previous research. Pelargonic acid (5%) controlled weeds similar to clove oil (2011 and 2012) and d-limonene (2013), with cool-season weed control efficacy being inconsistent among all herbicides. Onion yield response to weed control from any of the herbicides, including pelargonic acid, was also inconsistent. Pelargonic acid does not offer any weed control advantage over other herbicides derived from natural sources in organic onion production.