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The goal of this project is to test anaerobic soil disinfestation (ASD) as an economic alternative to methyl bromide (MeBr) for US growers; using strawberry (coastal California) and pepper/eggplant double crop (southeast Florida) as model production systems. We propose to manipulate different carbon sources, application methods, irrigation techniques, tarp materials, and timing/length of the tarping period to optimize control of key soilborne pathogens and nematodes. Further we will test a model that predicts the creation of anaerobic conditions and hence pathogen suppression under different soil conditions. The economic feasibility of ASD compared to MeBr treatments will also be assessed for each production system.<P> To meet this goal we have the following objectives. <ol> <LI>Form a research/extension/grower network to evaluate research findings and select the most viable options of ASD for on-farm testing in strawberry production systems in the central and the south coast of California and in the southeast coast of Florida. <LI>Optimize ASD methods for suppressing Verticillium dahliae and selected weeds in CA strawberry production, and for controlling root-knot nematodes (Meloidogyne spp.) and nutsedge (Cyperus spp.) in vegetables on the southeast coast of Florida. <BR>Hypothesis 2a): Pathogen and weed suppression will be achieved by an appropriate combination of length of tarping period, residue and other C source inputs, and irrigation.<BR> Hypothesis 2b): Tarping time needed will be reduced by selecting periods when soil temperatures are warmest and readily available C sources are added. <BR>Hypothesis 2c): When optimized ASD will be as effective as MeBr at pathogen, weeds and nematode suppression.<LI>Evaluate economic performance of ASD methods in comparison with MeBr fumigation. Hypothesis 3a): ASD is an economically viable alternative to MeBr under California coastal conditions and Florida conditions.<LI>Develop and validate a simulation model for ASD to help optimize tarping period and C inputs for different soils, temperatures and water regimes. <LI> Disseminate information on ASD methods to strawberry growers in the central and the south coast of California and vegetable growers in Florida.
Non-Technical Summary: Anaerobic soil disinfestation (ASD), an ecological alternative to methyl bromide (MeBr) fumigation, was developed in the Netherlands and Japan where it is used to control soilborne pathogens and nematodes in strawberries, tomatoes and other vegetables. Most biologically-based pest management systems target one or a few pests only, yet ASD affects a broad range of pest types and species making it functionally equivalent to current fumigant-based pest management from a grower perspective. California and Florida account for 78% of MeBr use in the US. The goal of this project is to test ASD as an economic alternative to MeBr for US growers; using strawberry on coastal California and pepper/eggplant double crop in southeast Florida as model production systems. <P> Approach: For objective 1, the project team will consult closely with four growers from the central coast and the south coast of CA to help select the most promising ASD options for strawberry production in the area, and to carry out on-farm trials. For objective 2, there will be 3 phases of experimentation. In phase 1, replicated pot experiments with different C sources, tarping materials and periods, and temperatures will be carried out in greenhouse facility at UCSC. Using data from the pot experiments, the precise design of the field experiments in CA and FL will be determined by group discussion. In phase 2, between June and September 2008, selected ASDs will be compared in replicated field experiments at two California sites and one Florida site. In CA, a buried inoculum retrieval method will be used to demonstrate suppression of V. dahliae and weeds by ASDs. During ASD treatment, soil Eh, soil temperature, and soil moisture at 15 cm will be monitored with sensors connected to a data logging system. After ASD, strawberries will be transplanted in November 2008. Fruit yield of strawberries will be measured weekly during the harvest season. The field trials in FL will be conducted in a USDA-ARS research farm in Fort Pierce. Pre-treatment soil samples will be taken to determine base line nematode and weed populations. ASD will begin in late summer 2008 and a bell pepper crop will be planted in September, and soil monitoring, sampling and analysis done as in CA. Phytotoxicity, plant growth measurements, weed and disease assessments, and nematode assays will be taken every 30 days until harvest. Peppers will be harvested up to three times. After peppers, eggplant will be planted into the existing beds and the assessments described for the pepper will be performed. In phase 3, in the 2009-2010 season, the most effective and feasible ASD option will be chosen from the 2008-2009 experiments and compared against the standard MeBr + chloropicrin fumigation treatment in field trials at two California sites and one Florida site. For objective 3, the costs of the most efficient ASD option will be determined from the field studies. Projected income for ASD and MeBr methods will be calculated based on yields realized in the field trials and current market prices for the regions under study. The estimated net returns to each of the management options for each location and farm size will be calculated under a range of price scenarios to test for economic feasibility. For objective 4, data collected on soil Eh and V. dahliae mortality in pot experiments will be used to develop an Eh degree-day model. The simulation model Denitrification-Decomposition (DNDC) and the Eh degree-day model will be integrated to estimate the required tarping period under many different scenarios. The integrated model will be validated with data from field trials. For objective 5, we will disseminate results using a combination of field day demonstrations, distribution of newsletters, and a series of workshops. Evaluation of the success of these efforts will be conducted each year and will include a qualitative assessment by interviewing all project participants and other key informants.