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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATED WEED MANAGEMENT SYSTEMS FOR ORGANIC AND CONVENTIONAL CROPS OF THE SOUTHEASTERN COASTAL PLAIN

Location: Crop Protection and Management Research

Title: Integrated systems of weed management in organic transplated vidalia sweet onion production

Authors
item Johnson, Wiley
item Langston Jr, David -
item Maclean, Daniel -
item Sanders, F -
item Torrance, Reid -
item Davis, Jerry -

Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 5, 2011
Publication Date: May 5, 2012
Citation: Johnson, W.C., Langston Jr, D.B., MacLean, D.D., Sanders, F.H., Torrance, R.L., Davis, J.W. 2012. Integrated systems of weed management in organic transplanted vidalia sweet onion production. HortTechnology. 22:64-69.

Interpretive Summary: Weed control in organic Vidalia® sweet onion is costly and limits expansion of the production system. Field experiments were conducted from 2008 through 2010 near Lyons, GA to develop integrated weed management systems for organic Vidalia® sweet onion production. Treatments were all possible combinations of summer solarization, cultivation with a tine weeder, and treatment with a clove oil herbicide. Plots were solarized with clear plastic mulch during the summer fallow period prior to transplanting onion. Cultivation treatments were twice at 2-wk intervals, four times at 2-wk intervals, and a non-cultivated control. Herbicide treatments were clove oil plus vinegar, clove oil plus an emulsified petroleum oil insecticide used as an adjuvant, and a non-treated control. ‘Savannah Sweet’ onion were transplanted in early-December each year, with cultivation and herbicide applications events occurring the following January and February. Onion were harvested the following spring. A sub-sample of harvested onion were stored in a controlled atmosphere storage facility to evaluate treatment effects on diseases of stored onion. Summer fallow solarization did not control the cool-season weeds present in these trials. Cultivating transplanted onion with a tine weeder effectively managed cutleaf eveningprimrose and swinecress, and improved onion yields in two of three years. There was little difference in overall performance between two cultivations and four cultivations with the tine weeder. The one year of marginal weed control with the tine weeder was due to persistently wet soils during winter months that inhibited optimum performance of the implement. Clove oil, combined with vinegar or an emulsified petroleum oil insecticide, provided marginal weed control and had no effect on onion yield. Diseases of stored onion were not affected by any of the treatment combinations.

Technical Abstract: Field experiments were conducted from 2008 through 2010 near Lyons, GA to develop integrated weed management systems for organic Vidalia® sweet onion production. Treatments were a factorial arrangement of summer solarization, cultivation with a tine weeder, and a clove oil herbicide. Plots were solarized with clear plastic mulch during the summer fallow period prior to transplanting onion. Cultivation treatments were twice at 2-wk intervals, four times at 2-wk intervals, and a non-cultivated control. Herbicide treatments were clove oil plus vinegar, clove oil plus an emulsified petroleum oil insecticide used as an adjuvant, and a non-treated control. ‘Savannah Sweet’ onion were transplanted in early-December each year, with cultivation and herbicide applications events occurring the following January and February. Onion were harvested the following spring. In addition to yield measurement, a sub-sample of harvested onion were stored in a controlled atmosphere storage facility to evaluate treatment effects on diseases of stored onion. Summer fallow solarization did not control the cool-season weeds present in these trials. Cultivating transplanted onion with a tine weeder effectively managed cutleaf eveningprimrose and swinecress, and improved onion yields in two of three years. There was little difference in overall performance between two cultivations and four cultivations with the tine weeder. The one year of marginal weed control with the tine weeder was due to persistently wet soils during winter months that inhibited optimum performance of the implement. Clove oil, combined with vinegar or an emulsified petroleum oil insecticide, provided marginal weed control and had no effect on onion yield. Diseases of stored onion were not affected by any of the treatment combinations, although overall incidence of diseases of stored onion was higher in 2010 compared to other years. This corresponds with the one year of marginal weed control with the tine weeder, suggesting that the presence of weeds may be a factor related to disease incidence during storage.

Last Modified: 9/23/2014
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