Alternative Management Practices to Reduce Soil Fumigant Use: A Meta-Analytic Approach.

Eliminating soil-borne pathogens, nematodes and weeds prior to transplantation is crucial for achieving high yields in crops such as strawberries, tomatoes, carrots, potatoes, grapes, almonds and walnuts.  Today, this is largely achieved by 4 fumigant chemicals: chloropicrin, 1,3-dichloropropene, metam potassium & metam sodium, collectively used at ~30 million lbs/year in California. However, their toxicity, carcinogenicity, high volatile organic compound (VOC) emissions and frequent exposures of the public and field workers are leading to increasing regulatory restrictions on their use in California and globally. The research effort to find effective non-fumigant methods to control these pests has focused on several management practices: solarization, steam, heat, biofumigation with isothiocyanate-releasing Brassica material, anaerobic soil disinfestation, grafting & resistant rootstocks, soil-less culture, host/non-host crop rotation, biological control agents, and non-fumigant chemicals.  However, variability in the success of these techniques among studies complicates our understanding of their efficacy.

Meta-analysis is a statistically-rigorous method for determining overall effect sizes and sources of variation between studies with similar experimental design.  Extensive literature searches & article screening have yielded ~600 studies on the crops listed above which compare one or more of the management practices directly with a fumigant treatment and report the resulting yield or level of pest suppression achieved.  We are currently entering these results and the experimental conditions under which they were obtained, and cleaning-up the data as necessary to allow direct comparisons between studies.  Our poster will present results of the meta-analysis and provide insight on the efficacy of these practices relative to fumigation treatment.

Funded by: California Department of Pesticide Regulation, Sacramento, CA (contract 12-C0069)