# The Current State and Future Potential of Microbial Control of Scarab Pests
## 10 Future Advancements
### Delivery Systems  
A major issue with using entomopathogens for biocontrol in soil systems is the ability of the pathogens to effectively disperse throughout the soil and make contact with target hosts. Entomopathogenic fungi must penetrate the insect cuticle at high concentrations to cause mortality and this requires a homogenous distribution and high concentration of conidia in the soil. For this reason, granular formulations, which consist of conidia-packed granules that can easily be mixed into soil, are preferable. Most fungal products consist of conidia and spores, but certain fungi, including _Metrahizium_ species, are also able to produce microsclerotia, which is a more resistant fungal stage that is less susceptible to environmental stressors and the presence of fungicides [329; 330; 331]. This increases their storage capacity, stability in the environment, and use in systems that require fungicide applications. It also increases their ability to be produced as granular formulations or seedcoats, which increase their infectivity in the field [332, 333, 334]. Recently, a method for producing microsclerotia of _B. bassiana_ has also been developed [335]. One of the most efficient ways to disperse entomopathogens is to let the insects do it themselves. This is particularly helpful when populations are patchy, their habitats are not well-known or are difficult to treat, such as soil systems. The simple, yet effective, method of autodissemination has been useful for distributing insecticides [336, 337], growth regulators [338, 339, 340], and microbes [341, 342, 343, 344, 345] for a range of insect pest species. For entomopathogens, autodissemination can increase individual mortality by improving pathogen contact with hosts, but it can also increase population-level infection rates through the transmission of pathogens between individuals, creating the potential for localized epizootics to occur. Autodissemination systems typically use some kind of attractant to lure adult insects into a trap where they are exposed to a microbial formulation. Adults then disperse, distributing the pathogen to feeding and mating sites, either as infected vectors or by carrying the microbes on their cuticle. Autodissemination systems have been tested on Japanese beetle, using commercial formulations of _M. anisopliae_ and _M. brunneum_[346, 347]. In the [PERSON] et al. [347] study, the traps increased the mortality of individual beetles that were directly exposed but also beetles that mated with infected individuals. These traps have also been found effective for infecting _Oryctes_ species with _M. anisopliae_, with one study showing 66.7% mortality of trapped beetles, but more importantly, 91% larval mortality in areas where the beetles transferred to spores to breeding sites [348, 349]. _Metrahizium_ autodissemination traps have also been effective on sorghum chater (_Pachmoda interrupta_) populations in Ethiopia [350, 351]. Although bacoloviruses have been successfully used in autodissemination traps for lepidopterans [60, 352, 353, 341], they have not been attempted with scarab-specific viruses. The autodissemination of entomopathogenic nematodes has also been proposed for Japanese beetle [354] but has yet to be tested. To our knowledge, no microsporidan species have been tested in autodissemination traps. Nanoparticles also offer tremendous potential for increasing the distribution and infectivity of entomopathogens. Nanoparticles made from _B. thuringiensis_ culture have been shown to be more virulent [355, 356], and while the association of fungal spores/conidia with nanoparticles is less developed, nanoparticles containing _B. bassiana_ and _M. anisopliae_ have been created [357]. Nanoparticles of _Nomuraaez nleyi_ have been shown to increase virulence against the potato tuber moth under lab and field conditions [358]. Double-stranded DNA and dsRNA have also been used in conjunction with nanoparticles to create non-viral gene delivery systems in insects [359, 360, 361].