Relationship Between Drosophila suzukii and Postharvest Disorders of Sweet Cherry (Prunus avium)

Abstract

Spotted wing drosophila, Drosophila suzukii, utilizes intact ripe fruits for oviposition and larval development. Sweet cherry (Prunus avium) and D. suzukii share a saprophytic microbial community, or microbiome, that colonizes the interior and exterior of the fruit, which benefits the nutrition and development of the flies. Some of the microbes, specifically yeast species, are also reportedly associated with a newly described slip-skin-like disorder of sweet cherries. In British Columbia (BC), Canada, contact-based insecticides and fungicides are applied to sweet cherry to suppress D. suzukii populations and cherry diseases, respectively. To date, no resistance to the organophosphate insecticide, malathion, in D. suzukii field or laboratory populations has been reported. Laboratory bioassays with malathion-incorporated diet determined that when microorganisms associated with the D. suzukii microbiome were sterilized with potassium metabisulfite (KMS), survival of the flies was significantly affected. These findings led to speculation that malathion residues on cherry fruit may be degraded due to the greater presence of yeast species that are spared as a result of selective fungicide use patterns in cherry orchards. In orchard trials, KMS was shown to be effective in suppressing the surface yeast counts on cherry, but this did not impact symptoms of slip-skin-like disorder. Based on these findings, it is recommended that other products functioning as systemic biocides need to be investigated to address these two microbial-connected pest management concerns in sweet cherries.