|SHENNAN, CAROL - University Of California|
|MURAMOTO, JOJI - University Of California|
|MARGHERITA, ZAVATTA - University Of California|
Submitted to: International Conference on Methyl Bromide Alternatives and Emissions Reductions
Publication Type: Proceedings
Publication Acceptance Date: 10/11/2014
Publication Date: 11/9/2014
Citation: Shennan, C., Muramoto, J., Margherita, Z., Mazzola, M. 2014. Non-fumigant approaches for controlling Fusarium wilt and charcoal rot of strawberry. International Conference on Methyl Bromide Alternatives and Emissions Reductions. 11.1-11.4.
Interpretive Summary: Soil-borne disease management without chemical fumigants remains a major challenge for strawberry production in California, and modifications to existing regulations are likely to intensify this challenge by further limiting availability of fumigants on a large percentage of strawberry acreage. 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. Anaerobic soil disinfestation has been consistently effective in the control of Verticillium wilt of strawberry when rice bran was used as the carbon input. However, ASD with or without the application of mustard seed meal provided significant control of charcoal rot caused by the fungus Macrophomina phaseolina resulting in enhanced strawberry yields. Mustard seed meal alone provided incomplete control of charcoal rot and correspondingly lower yields relative to ASD, but yields were still higher than that attained in the grower standard control. In these trials, ASD treatments and MSM application even at 3t/ac did not suppress the incidence of Fusarium wilt. However, yields were greater for the strawberry cultivar San Andreas than Albion, and the former did not exhibit symptoms of disease indicating this varieties resistance to the Fusarium wilt pathogen Fusarium oxysporum f. sp. fragariae. Trials are being repeated with refinements to determine whether greater pathogen control can be achieved. This work demonstrates that an integrated approach including use of resistant varieties is important as a non-fumigant strategy.
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. Anaerobic soil disinfestation (ASD) conducted using rice bran as the carbon input has provided effective control of multiple strawberry soil-borne diseases including Verticillium wilt in field evaluations. However, control of Fusarium wilt using the same protocol has yielded inconsistent results. ASD failed to control Fusarium wilt caused by Fusarium oxysporum at the Monterey Bay Academy (MBA) site in Watsonville, CA. Yet studies elsewhere have shown that ASD can control this disease under higher soil temperatures (Momma et al., 2013). This emerging lethal disease of strawberries has been spreading across the main strawberry production areas in California. Similarly, charcoal rot caused by Macrophomina phaseolina is another pathogen of increasing importance in CA strawberries and while ASD has been found to control this pathogen in FL, control under CA conditions needs to be documented. As previously observed for other locations, application of ASD with RB or use of mustard seed meal (MSM) led to distinctly different microbial community profiles which may be important for disease control. A doubling of yields relative to the grower standard, and a reduction in the incidence of disease caused by M. phaseolina, was achieved in response to ASD conducted using rice bran at 9 t/ac. MSM applied at 2t/ac failed to control M. phaseolina and resulted in yields that were more than 20% below the ASD-RB9 yields, although still substantially higher than the grower standard. A combination of phytotoxicity following transplanting, and subsequent salinity damage due to high nitrate levels over the winter may have reduced yields in the MSM treatment. ASD and MSM treatments did not suppress Fusarium wilt incidence. There is evidence that when soil temperatures are adequately high ASD with RB as a carbon source may effectively reduce both Fusarium wilt and charcoal rot in strawberry in CA, but may not be capable of providing complete control.