Temporally separated events associated with microbiome of Drosophila suzukii (Matsumura) and sweet cherries in B.C., Canada
Citation
M.M. Ayyanath, C.L. Zurowski, I.M. Scott, D.T. Lowery,M.C. Watson, D.T. O’Gorman, J.R. Úrbez-Torres, P. Haag and K.E. Mackenzie. (2017) Temporally separated events associated with microbiome of Drosophila suzukii (Matsumura) and sweet cherries in B.C., Canada. Canadian Webinar Series – Third Session: Spotted-wing Drosophila (Fruit Fly) – February 9, 2017.
Résumé en langage clair
A probable imbalance created between interior and exterior resident microbes occurs at the time when saturation of the fruits with sugars permits minimal penetration of pesticides yet promotes microbial activity. Combinations of low internal calcium and higher temperatures and humidity commonly reached during the late growing season (late Aug. - mid Sept.) are among conditions known to promote fermentation. These conditions also could have resulted in a potential physiological disorder expressed as a classical post-harvest problem having slip-skin-like symptoms caused by microbial enzymes lacerating the junction between the pulp/mesocarp and rind/epicarp. Similar to grape sour rot, possible varietal differences in sweet cherries, such as tight clusters and thickness of the skin, would make them more susceptible to this physiologically-triggered postharvest disorder. Suppressing Spotted Wing Drosophila (2-3 weeks pre-harvest) and managing on-field slip-skin-like postharvest disorder (1 week pre-harvest to 1 week postharvest), which are occurring at temporally separate periods, may both be achieved by controlling the microbial levels on and within fruit via physiologically means using commercially available systemic chemical biocides and/or cultivation practices, such as judicious use of nitrogen fertilizers since excess use of nitrogen could heighten microbial cues by triggering the fermentation process inside the fruit.
Résumé
Spotted wing drosophila (SWD), Drosophila suzukii (Matsumura) utilizes intact ripe fruits for the perpetuation of its immature forms. Contact based insecticides are effective in suppressing SWD either by causing mortality or inducing avoidance. Increased degradation of malathion, an contact based organophosphate insecticide, occurred under laboratory conditions with the addition of males in the experiments suggesting the involvement of microbiome hastens the degradation process. This microbiome, saprophytic in purpose, exists in and outside the fruits SWD visits, and also is responsible for a newly reported postharvest slip-skin-like disorder in sweet cherries in British Columbia (BC), Canada. Potassium metabisulphite (KMS) was used in the laboratory experiments to suppress microbiome-induced malathion degradation, and also to suppress the surface yeast counts in on-field experiments to manage slip-skin-like disorder. KMS at 0.1x the recommended rate resulted in arresting microbiome-induced malathion degradation in half, suggesting the role of plant-dwelling microbiome in the reduction of insecticidal efficacy. KMS was effective in suppressing the surface yeast counts but had no influence on slip-skin-like disorder caused by endophytic microbiome of cherries due to its non-systemic mode of entry. Currently, there are no effective registered products functioning as a systemic biocide to address these two microbial-connected, yet temporally disconnected events in sweet cherries.