An invasive variant of the pasture mealybug Heliococcus summervillei (Hemiptera: Pseudococcidae) and its obligate endosymbiont Tremblaya phenacola (Enterobacterales: Enterobacteriaceae).

Abstract

The pasture mealybug Heliococcus summervillei Brookes (Hemiptera: Pseudococcidae) is the cause of extensive pasture dieback in Australia and is an emerging biosecurity threat to pasture and crop grasses in the Americas. In this study, we present a morphological and molecular comparison of contemporary Australian specimens of H. summervillei and the primary bacterial endosymbiont Candidatus Tremblaya phenacola Gruwell (Enterobacterales: Enterobacteriaceae) with reference to historical and published specimens. Molecular analyses were conducted using three host nuclear markers (18S, 28S-D2, dynamin) and the universal bacterial marker (16S V3-V4 region). Our results identify a new, highly invasive variant of H. summervillei associated with the ongoing dieback outbreak in Australia. This work uses 16S barcoding to support host-based morphological and molecular approaches to differentiate this new variant from the type specimens.