Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/28/2016
Publication Date: 9/14/2016
Citation: Mazzola, M. 2016. Multiplicity of mechanisms govern efficacy of anaerobic soil disinfestation for soil-borne disease control. Symposium Proceedings. p. 9.1-9.10.
Interpretive Summary: Soil-borne disease management without chemical fumigants remains a major challenge for many crop production systems including strawberry and tree fruits. Anaerobic soil disinfestation (ASD) has demonstrated promise as an alternative to soil fumigation for the control of soil-borne diseases. ASD involves the generation of an anaerobic environment through a combination of flooding and addition of a carbon source to the soil system. The current studies demonstrated that ASD provides pathogen suppression and corresponding disease control through a diversity of mechanisms. Production of volatile chemistries in response to both ASD can suppress certain pathogens, however our findings demonstrate that soil biology can also contribute significantly to overall disease control attained. In fact, suppression of certain diseases, including Fusarium wilt of strawberry, appears to rely predominant on enhanced activity of certain bacteria in ASD-treated soils. In apple, orchard grass proved a superior ASD carbon source input for control of the pathogen complex that incites apple replant disease. Efficacy of the grass-ASD treatment for disease control was also associated with specific changes in the soil microbial community, with amplification of certain bacteria and fungi that are known to have biological control activity. ASD treatments promote a soil biological community that is more resilient to re-infestation by plant pathogenic organisms and may provide a more sustainable alternative to the use of fumigants for the control of soil-borne diseases.
Technical Abstract: Studies demonstrated that carbon input type influenced control of various fungi, oomycetes and plant parasitic nematodes with anaerobic soil disinfestation (ASD). Findings implicated multiple mechanisms may contribute to the overall level of disease control attained. In strawberry field trials, ASD conducted with 20 t ha-1 rice bran (RB) as the carbon input provided pathogen control and significantly increased yields relative to a non-treated control. In addition, for three of four trials this ASD treatment resulted in yields that were statistically equivalent to the fumigation control. Effective, but not ineffective, ASD carbon inputs induced changes in the soil microbiome that persisted through the growing season. Interestingly, the role of anaerobicity in disease suppression was questioned as incorporation of RB with or without water provided the same level of disease control and similar shifts in composition of the soil microbiome. ASD-induced suppression of pathogens associated with apple replant disease also was associated with amplification of specific elements of the soil microbiome. In apple, orchard grass was the most effective ASD carbon input for control of replant disease and was accompanied by transformation of the soil microbiome and generation of biologically active volatiles. California strawberry growers are already adopting ASD as a soil-borne disease control option in strawberry production, with greater than 500 ha treated during the 2015 growing season. Continued progression in grower adoption will require further optimization of the protocol, identification of additional cost effective carbon inputs, and modification of the system to generate control of, to date, insensitive pathogens such as Fusarium oxysporum f. sp. fragariae.