Filth Flies, Flowers and Food: Pollination by Flies (Calliphoridae) Does Not Affect the Strawberry Microbiome.

Blow flies can be used as alternative pollinators to honeybees for several crops. However, they can potentially vector harmful bacteria to surfaces on which they land. Therefore, there is a risk that blow flies may contaminate flowers, and thereby fruit, with human pathogens. Growers, supermarkets and consumers may therefore have concerns about food safety. To address these concerns, we asked: (1) do fly visits result in altered bacterial communities on flowers, and if so, (2) do these altered communities persist to the fruit stage? We exposed strawberry flowers to “clean” blow flies and flies that had contacted a common environmental contaminant (cow manure). Using a 16 S rRNA gene amplicon sequencing approach, we evaluated the impact of the blow fly visits on the flower and fruit microbiomes. We found that the fruit microbiome was not impacted by our treatments, specifically, no shared amplicon sequence variants were found in both the manure and the resulting fruit that developed after pollination by a manure-exposed fly. This suggests that fly pollination is unlikely to pose a risk to human health. Our study may help to alleviate concerns from growers and consumers of using flies as managed pollinators in the agrifood system.