# The Current State and Future Potential of Microbial Control of Scarab Pests
## 4 Bacteria
### Serratia Species  
Several _Serratia_ species, a genus of non-spore-forming bacteria in the family Enterobacteriaceaeiaceae, have been documented to infect several scarab species [48]. In 1981, two _Serratia_ species were isolated from a declining population of New Zealand grass grubs (_C. zealandatica_). _S. entomophila_ and _S. proteamaculans_ were implicated in producing amber disease in this population [49], which causes larvae to stop eating or producing digestive enzymes, giving the grubs a translucent coloration and eventually weakening them so that the bacteria can enter the hemocoel [19]. Grubs die from septicemia within months of infection [48; 50]. Pathenogenic and non-pathenogenic strains of _S. entomophila_ and _S. proteamaculans_ are found in the field and is dependent on the presence of a specific plasmid that carries the sep and afp genes required for virulence [51]. While these two species appear to be exclusively toxic to _C. zealandatica_ and _Pyronota_ species [52; 53], other Serratia species are known to infect other scarabs. _S. marcscreens_ was isolated from May beetles in New Zealand (_M. melolontha_) [54], and several strains were isolated from May beetles in Mexico, showing differing degrees of toxicity [55]. A strain of _S. entomophila_ was also cultured from a date palm scale (_Parlatoria blanchardi_) in Mexico and was found to cause significant mortality in intraceolomic inoculations and feeding trails with various _Phylolphag_ and _Anomala_ species [56]. In the U.S., _Serratia_ species have only been found in Japanese beetle and masked chafer grubs in Kentucky, albeit at low levels [57; 58].  
_Serratia entomophila_ was developed as a commercial product in New Zealand in the 1980s. Despite high efficacy, the first incarnation, called Invade and produced by Monsanto, had a short shelf-life and required specialized application. Invade was eventually taken off the market [59], but in the early 2000s, a much more stable granular formulation, called Bioshield, was developed and is still currently available in New Zealand as a liquid formulation [59; 60]. While there are no data available on the efficacy of Bioshield, lab studiestesting _S. marcescens_ and _S. entomophila_ strains from Mexico documented high mortality in May beetles (_P. blanchardi_) and leaf chafers (_A. donovani_) after oral inoculation [55; 56].  
The distribution of _Serratia_ species in the U.S. is largely unknown, as is their ability to produce natural epizootics. However, studies from New Zealand show that field applications of commercially available _S. entomophila_ readily create established populations [59; 61]. In fact, Bioshield's documentation claims that _Serratia_ populations may last 3 to 5 years after application. More work is needed to understand the ecology of _Serratia_ species and their role as insect pathogens in the U.S., but given their ability to recycle in the soil, they may become a viable option for novel scarab biocontrol in the future. One potential drawback, is that some strains of _S. marcenscens_ infect honey bees [62], which cautions that the selection of a scarab-specific _Serratia_ species must be an important aspect of future product development to reduce non-target effects.