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: Mazzola, M., Shennan, C., Muramoto, J. 2012. Application Sequence and soil biology influence anaerobic soil disinfestation induced disease suppression. Proceedings of International Research Conference on Methyl Bromide Alternatives. 57:1-3. Interpretive Summary: Anaerobic soil disinfestation (ASD) and mustard seed meal soil amendments have been used to control a variety of soil borne plant diseases. In ASD, an anaerobic soil environment is created by flooding of soil in concert with the addition of a carbon source to promote growth of soil microorganisms. This in turn leads to the creation of organic acids by the anaerobic decomposition of the added carbon, and these acids are believed, in part, to provide disease control. Disease control in response to mustard seed meal amendments also requires the activity of soil microorganisms. As both methods alter soil biology and require soil biology to control plant diseases, it is possible that when the methods are integrated enhanced or diminished disease control could result depending upon the sequence of application and how this alters microbial populations. In these trials the growth of strawberry was monitored in a field soil when ASD and MSM were applied individually or in combination, with the order of application of these treatments as a variable. Although all treatments improved plant growth, when used in combination, only the sequence of ASD first followed by MSM application enhanced growth relative to the individual treatments alone. All treatments had distinct effects on soil microbial community composition but soil pH was lowered only in treatments in which ASD was last in the application sequence. It is possible that differences in soil biology, soil pH or soil fertility resulting from the treatment application sequence contributed to the variable plant growth response. A greater understanding of the soil biology that contributes to the activity of these disease control methods will be necessary to ensure the effective integration of these techniques as a disease management option.
Technical Abstract: Anaerobic soil disinfestation (ASD) and mustard seed meal (MSM) soil amendments can yield significant control of a diversity of soil-borne pests and pathogens. The mechanisms functional in disease suppression are diverse and with regard to MSM amendment, soil biology has been shown to have a significant or even primary role in the resulting disease control. As such, when applied collectively in an integrated approach these individual treatments have capacity to enhance or diminish the functional disease control mechanisms that operate in response to the independent methods. Studies were undertaken to assess the effect of application sequence on growth performance of strawberry in response to integration of ASD with MSM amendment and to determine the influence of soil biology on long-term ASD induced suppression of root infection by the oomycete pathogen Pythium ultimum. ASD treated soil was suppressive to root infection by the introduced isolate of P. ultimum, but suppressiveness did not develop in pasteurized soil that were treated with ASD prior to pathogen infestation. Plant growth was significantly improved in response to all ASD or MSM treatments relative to the control. However, MSM applied to soil two or three weeks after ASD treatment significantly improved strawberry growth relative to the individual treatments or when ASD was applied following MSM application. Effective use of ASD or its integration with other methods such as MSM requires an understanding of mechanisms of action to avoid the diminution or elimination of disease control activity, as was observed in trials where seed meal amendments preceded the application of ASD.