Does Unaspis euonymi (Comstock) (Hemiptera: Diaspididae) host Serratia symbiotica Moran (Bacteria: Enterobacteriaceae)?

Abstract

The euonymus scale Unaspis euonymi (Comstock) (Hemiptera: Diaspididae) is a pest of spindle that exhibits a strong preference for Euonymus, although it has been detected on at least 18 genera in 13 plant families (Buxus, Camellia, Celastrus, Daphne, Eugenia, Euonymus, Hibiscus, Ilex, Jasminum, Ligustrum, Lonicera, Olea, Pachistima, Pachysandra, Perychmenum, Prunus and Syringa) (Salisbury et al., 2013). Heavy infestation by this pest may lead to the death of the host plant and consequential loss of income from the cultivation of ornamental plants (Kaygin et al., 2008). U. euonymi is an armored scale insect originally from mild Eastern Asia and probably introduced into Europe in the 20th century (Pellizzari & Germain, 2010). Its lifecycle, depending on climate conditions, comprises two-three generations a year and the control measures to limit its diffusion mainly rely on the use of insecticides or the growing of resistant cultivars.

The insects can engage mutualistic interactions or symbioses with a variety of bacteria that can profoundly affect the host’s biology. Apart from obligate symbionts (maternally transmitted), a growing number of facultative or secondary symbionts (that can be horizontally transmitted) have been identified (Sandstrom et al., 2001, Moran et al., 2008). Despite not being essential for the host’s life cycle, this last type of symbiont can strongly influence their fitness (Oliver et al., 2003, Jaenike & Brekke, 2011). Additionally, the mutualistic association between insects and bacteria may play a role in the evolution of the latter as described for some groups of Entereobacteriaceae (Moran et al., 2005). A number of genomic and phylogenetic studies on mutualistic associations between Enterobacteriaceae and aphids, psyllids, scale insects, whiteflies, weevils and other insects have been reported (Lefevre et al., 2004, Thao & Baumann, 2004).

Here we report the identification of Serratia symbiotica (strain UESS2016) in U. euonymi adult females collected from Sofia (Bulgaria) in 2013.