Soil pest management in current California strawberry production: a review

Coastal California remains one of the world's primary strawberry growing regions with approximately 15,000 ha annually in fruit production. Since the phase out of methyl bromide fumigation, approximately 85% of California fields have been treated with alternative soil fumigants, while the remainder is managed without fumigation. In the last decade, the primary biotic stress production problems have been due to soil-borne pathogens Verticillium dahliae, Fusarium oxysporum f. sp. fragariae, Macrophomina phaseolina and the perennial weed Cyperus esculentus. With increasing costs of fruit production, and lack of effective control options, management of these soil-borne pests has been inadequate. Research and extension efforts have focused on cost-effective approaches to sustain production in the presence of these and other pests. Optimization of use of available fumigants targeted improved distribution of drip applied products under impermeable tarps, timing of fumigation, precision application based on need during shank injections, and evaluation of new fumigants in combination with other tools. Non-fumigant approaches have included the development and use of resistant cultivars, soil solarization, steam application, crop rotation, anaerobic disinfestation, soilless media, and use of natural biocides. Additionally, growing strawberry in cooler soils in the winter delays disease development and weed competition and can allow fruit production in infested soils. Soil pH adjustment and infested crop termination have also been evaluated. Review of current practices and on-going research emphasizes the need for integrated, site-specific programs based on efficacy, cost, and environmental impacts to maintain strawberry production in the presence of soil-borne pathogens and weeds.