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Interactions among Cultivation, Weeds, and a Biofungicide in Organic Vidalia® Sweet Onion

Published online by Cambridge University Press:  11 September 2017

W. Carroll Johnson III ,
Bhabesh Dutta ,
F. Hunt Sanders Jr.  and
Xuelin Luo
W. Carroll Johnson III*
Affiliation:
Research Agronomist, USDA-ARS, Tifton Campus, P.O. Box 748, Tifton, GA 31793-0748
Bhabesh Dutta
Affiliation:
Assistant Professor and Former Disease Management Specialist, Department of Plant Pathology, University of Georgia, Tifton Campus, Tifton, GA 31793
F. Hunt Sanders Jr.
Affiliation:
Assistant Professor and Former Disease Management Specialist, Department of Plant Pathology, University of Georgia, Tifton Campus, Tifton, GA 31793
Xuelin Luo
Affiliation:
Research Statistician, University of Georgia, Tifton Campus, Tifton, GA 31793
*
*Corresponding author’s E-mail: [email protected]
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Abstract

Weed management in the organic Vidalia® sweet onion production system is largely dependent on multiple cultivations with a tine weeder. Earlier research suggested cultivation with a tine weeder did not predispose onion bulbs to infection during storage. Trials were conducted from 2012 through 2014 near Lyons, GA, to determine the interactive effects of cultivation, weed removal, and a biofungicide on weed densities, onion yield, grade, and diseases of stored onion. Cultivation twice or four times at biweekly intervals with a tine weeder reduced densities of cutleaf evening-primrose, lesser swinecress, and henbit compared with the noncultivated control, although weeds surviving cultivation were very large and mature at harvest. Cultivation generally improved onion yields over the noncultivated control, except in 2014, when baseline weed densities were high and weeds surviving cultivation were numerous. Weeds removed by hand weeding improved onion yields, but that effect was independent of cultivation. Four applications of a biofungicide derived from giant knotweed had no effect on onion yield. Cultivation had no effect on incidence of the fungal disease botrytis neck rot, with inconsistent effects on the bacterial diseases center rot and sour skin. Weed removal with hand weeding did not affect diseases of stored onion. The biofungicide had no effect on diseases of stored onion. These results demonstrate the limitations of cultivation when cool-season weed infestations are dense. With no interactions among main effects, weed control and onion yield response to cultivation and hand weeding are independent. Cultivation for weed control is much less costly than hand weeding. With no interaction between the cultivation and weed removal main effects, it is not necessary to supplement tine weeder cultivation with costly hand weeding.

Keywords

Cutleaf evening-primrose, Oenothera laciniata Hillgiant knotweed, Reynoutria sachalinensis (F. Schm.) Nakaihenbit, Lamium amplexicaule Llesser swinecress, Coronopus didymus (L.) Sm.dry-bulb onion, Allium cepa L.Giant knotweed extractmechanical weed controlorganic weed controlReynoutria sachalinensis extracttine weeder
Type
Weed Management-Other Crops/Areas
Information
Weed Technology , Volume 31 , Issue 6 , December 2017 , pp. 890 - 896
Copyright
© Weed Science Society of America, 2017 

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Footnotes

a

Current address of third author: Field Market Development Specialist, Valent Biosciences, Tifton, GA 31794.

Associate Editor for this paper: Mark VanGessel, University of Delaware.

References

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