Microbial associates of the vine mealybug Planococcus ficus (Hemiptera: Pseudococcidae) under different rearing conditions.

Sap-feeding insects harbor diverse microbial endosymbionts that play important roles in host ecology and evolution, including contributing to host pest status. The vine mealybug, Planococcus ficus, is a serious pest of grapevines, vectoring a number of pathogenic grape viruses. Previous studies have shown that virus transmission is abolished when mealybugs are raised in the laboratory on potato. To examine the possible role of microbial symbionts in virus transmission, the archaeal, bacterial, and fungal microbiota of field and laboratory P. ficus were characterized using molecular and classical microbiological methods. Lab and field colonies of P. ficus harbored different microbiota. While both were dominated by the bacterial obligate nutritional symbionts Moranella and Tremblaya, field samples also harbored a third bacterium that was allied with cluster L, a lineage of bacterial symbionts previously identified in aphids. Archaea were not found in any of the samples. Fungal communities in field-collected mealybugs were dominated by Metschnikowia and Cladosporium species, while those from laboratory-reared mealybugs were dominated by Alternaria and Cladosporium species. In conclusion, this study has identified a diverse set of microbes, most of which appear to be facultatively associated with P. ficus, depending on environmental conditions. The role of various members of the mealybug microbiome, as well as how the host plant affects microbial community structure, remains to be determined.