Project Number: 2094-21220-001-02-R
Project Type: Reimbursable
Start Date: Sep 1, 2012
End Date: Aug 31, 2016
Anaerobic soil disinfestation (ASD) has demonstrated significant potential as an alternative to methyl bromide (MeBr) for the control of soilborne pathogens and nematodes. This project seeks to validate the efficacy of ASD as a MeBr alternative alone or when integrated with mustard seed meal (MSM) for control of significant soilborne diseases in two CUN cropping systems; pre-plant soil use for strawberry and tree fruit nursery production systems. These ASD systems can be utilized in urbanized areas where buffer restrictions limit the applicability of alternative fumigants and, unlike many other biologically-based alternatives, have a broad-spectrum of activity, impacting most pests that are currently controlled by MeBr:chloropicrin combinations. We have obtained consistently effective suppression of Verticillium dahliae in soils with ASD and achieved yields within 76-100% of MeBr and 95-120% of other chemical fumigants in California strawberry systems. Pre-plant application of MSM formulations has provided fumigant levels of soilborne disease control in apple production systems. Although efficacy has been demonstrated, adoption of these methods for disease control in these cropping systems requires optimization from a nitrogen management and economic perspective. Our goals are to fine tune the protocol to optimize and demonstrate efficacy and economic feasibility of ASD alone or when integrated with MSM for soilborne disease control in commercial scale field trials, garner a comprehensive understanding of the biological and chemical modes of action operative in MSM and ASD-induced pathogen suppression, and effectively disseminate this information through a variety of formats including production of webinars and an “ASD Manual for Strawberries”. Specific objectives are; 1) to fine-tune type and rate of carbon sources and N management for anaerobic soil disinfestation (ASD) in strawberry systems; 2) to demonstrate ASD in commercial scale trials and evaluate its effectiveness and economic feasibility in strawberries; 3) to examine integration of ASD and mustard seed meal (MSM) for control of soil-borne disease in apple nurseries as an alternative to methyl bromide fumigation 4) to determine whether changes in soil microbial composition are responsible for soil-borne disease suppression detected in response to ASD, and MSM; and 5) to disseminate ASD to California strawberry growers via workshop, field days, eXtension, and by publishing “ASD Manual for Strawberries".
1. Greenhouse studies will be conducted to evaluate different organic inputs at various rates to assess the optimal input in the application of anerobic soil disinfestation from both a resource utilization and disease control standpoint. Disease development will be monitored using culture based and molecular-based methods. 2. Based upon the results of the greenhouse trials, field experiments will be designed and implemented at three strawberry field locations in California. Disease development, growth and yield will be assessed. 3. Brassicaceae seed meal (BSM) and anerobic soil disinfestation (ASD)have demonstrated potential to control the diversity of pathogens that incite replant diseases in nursery and orchard settings. However, integration of these methods may enable a more cost effective disease control alternative with improved disease control efficacy. Controlled environment experiments will be conducted to determine minimum substrate application rates that yield effective disease control. In addition, the effect of application sequence of the two substrates on disease control and tree growth will be determined. Based upon these trials, the treatment yielding optimal disease control will be evaluated in field trials conducted at two nursery sites in Washington State. 4. To assess the role of soil biology in the suppressive activity of ASD and BSM treatments, these same studies will be conducted in pasteurized soil systems. The relative level of disease control attained in the natural and pasteurized soil systems should yield important information regarding the contribution of soil suppressiveness to the ASD/BSM induced disease control. Repeated measures of soil physical parameters of temperature, Eh and pH are taken to track physical changes that occur during the course of treatment especially with ASD. Volatile compounds produced during the incubation period will be examined using GC/MS analysis. Should data indicate a role for soil biology in the suppression of an introduced isolate of Phytophthora cactorum, Terminal Restriction Fragment Length Polymorphism (TRFLP) analysis will be utilized to examine the dynamics of soil biology in response to treatments. Should resulting T-RFLP profiles (bacterial or fungal)indicate a relationship between changes in population structure and disease suppression, pyrosequencing will be carried out to more clearly identify the changes in soil microbial populations in those treatment(s) that most efficiently yield a disease suppressive state. 5. We will disseminate results using a combination of site visits, electronic team meetings, on-farm and Research and Education Center field days, grower meetings, on-farm demonstrations, distribution of newsletters and research briefs, maintenance of an interactive project website, and a workshop series. The project website will be linked to key grower visited websites in each state. In year 3, a grower guide to ASD will be created and distributed through our workshops and local networks. These efforts will be targeted at growers, cooperative extension personnel,private pest control advisors,industry representatives and relevant state and federal agencies.