Non-fumigant strategies for soilborne disease control in California strawberry production systems

Authors: SHENNAN, CAROL - University Of California; MURAMOTO, JOJI - University Of California; FENIMORE, STEVE - University Of California; BOLDA, MARK - University Of California; DAUGOVISH, OLEG - University Of California; DARA, SURENDRA - University Of California; Mazzola, Mark; LAZAROVITS, GEORGE - A&l Canada Laboratories, Inc

Submitted to: Proceedings of International Research Conference on Methyl Bromide Alternatives
Publication Type: Proceedings
Publication Acceptance Date: 9/19/2012
Publication Date: 11/6/2012
Citation: Shennan, C., Muramoto, J., Fenimore, S., Bolda, M., Daugovish, O., Dara, S., Mazzola, M., Lazarovits, G. 2012. Non-fumigant strategies for soilborne disease control in California strawberry production systems. Proceedings of International Research Conference on Methyl Bromide Alternatives. 16:1-4.

Interpretive Summary: The development of effective environmentally sustainable alternatives to soil fumigation for disease management in strawberry production systems is a major challenge. A number of potential alternatives were evaluated in multiple field trials including the application of steam, anaerobic soil disinfestation and soil incorporation of mustard seed meals. Anaerobic soil disinfestation (ASD) was developed in Japan and the Netherlands as an alternative to soil fumigation and involves the generation of an anaerobic environment through a combination of flooding and addition of a carbon source to the soil system. Disease control is believed to result from the production certain volatiles that are generated by microorganisms that are active under anaerobic conditions. Application of ASD with or without mustard seed meal amendment resulted in fruit yields that were equivalent to that attained in response to soil fumigation. However, the treatments were less effective than fumigation for the control of weeds. The ASD and mustard seed meal treatments resulted in elevated populations of both fungi and bacteria in the soil environment, and these increased microbial populations may be associated with disease control. These treatments also resulted in very microbial populations of very distinct composition which varied significantly from the controls. Further evaluation of these microbial communities may yield understanding of how ASD and mustard seed meal amendments improve growth of strawberry and suppress soil-borne diseases. introduction of the pathogen. These data demonstrate that control of charcoal rot of strawberry in response to seed meal may require biological processes that are brought about by seed meal application to soil and is not a function of chemical activities alone.

Technical Abstract: Soilborne disease management without chemical fumigants is a major challenge for strawberry production in California. Current re-registrations and regulations are likely to intensify this obstacle by severely limiting availability of fumigants on a large percentage of strawberry acreage. A number of non-fumigant pre-plant strategies and there application as an integrated disease control strategy were evaluated in strawberry production systems. In two field trials marketable fruit yields in response to anaerobic soil disinfestation applied in concert with mustard seed meal amendment were statistically equivalent to that attained in response to pre-plant soil fumigation. However, anaerobic soil disinfestation alone or in combination with mustard seed meal was significantly less effective than soil fumigation for weed control, demonstrating the need for herbicide treatment on sites having an elevated weed density. Treatments had distinct effects on soil fungal and bacterial community composition as determined by terminal restriction fragment length polymorphism analysis. Elevated fungal and bacterial densities were detected in soils treated with anaerobic soil disinfestation or mustard seed meal amendments, indicating a potentially more competitive environment. This attribute may be important in the overall performance of these methods as a disease control alternative.