# The Current State and Future Potential of Microbial Control of Scarab Pests
## 5 Fungi
### Beauveria Species  
Strains of fungi in the _Beauveria_ genus represent some of the most widely used microbial agents for insect control [85]. _Beauveria bassiana_ is the most commonly used strain, and, in fact, was the first disease to be discovered in insects. It causes white muscarding disease, which almost destroyed the European silk industry in the 18 th and 19 th centuries when infection spread through captive silkworm (_Bombyx mori_) populations. _B. bassiana_ is widely distributed globally and alone can infect more than 700 different insect species [86; 87], including a variety of different scarab species all over the world. _B. bronginartii_ is another common species but one with a much narrower host range that is largely restricted to scarabs [88; 89]. Recently, six additional species of _Beauveria_, including: _B. majangensis_, _B. malawiensis_, _B. scarabaeidicola_, _B. songmingensis_, _B. subscarabaediicola_, _B. yumanensis_, were discovered in scarabs collected throughout China and Thailand and were placed in a _B. scarabaeidicola_ complex [90].  
_B. bassiana_ comprises about 34% of the commercially available mycoinsecticidal products worldwide [91]. There are currently four strains of _B. bassiana_ registered with the U.S. Environmental Protection Agency (EPA), HF23, GHA, ANT-03, and PPRI 5339, corresponding to over 45 different registered products. Several other formulations are available globally [36; 84]. Although _B. bassiana_ is generally very effective, with most studies showing about 70% mortality at high spore concentrations within 2-3 weeks after application [92; 93; 94; 95], its efficacy on scarab species is variable across strains and larval instars [95; 96; 97; 98; 99; 100]. _B. bronginartii_ appears to provide more consistent control of scarab pests than _B. bassiana_[101; 102; 103; 104; 105; 106], but it is only commercially available in European markets [5; 84]. Most of the species in the _B. scarabaeidicola_ complex and have not yet been tested extensively; however, [PERSON] et al. [90] did test these four of these species (_B. scarabaeidicola_, _B. subcarabaediicola_, _B. songmingensis_, and _B. yumanensis_) against the white-spotted flower chafer (_Protaeta brevitarsis_), and two non-scarabs, _B. mori_ and _Tenebrio molitor_. Species from the _B. scarabaediicola_ complex did not infect _B. mori_ or _T. molitor_ larvae but did produce ~45% mortality in _P. brevitarsis_ adults. Despite this, the mortality rates of species from the _B. bassiana_ complex were much higher for _P. brevitarsis_.  
Epizootics of _Beauveria_ strains have been widely reported for different insect pests [107; 108; 109; 110], including several scarab species [111; 42; 63; 81; 82; 107; 108; 42; 109; 110]. [PERSON] et al. [111] documented two epizootics in the New Zealand grass grub, involving both _B. bassiana_ and _B. bronginartii_, which resulted in 30% and 99% mortality. Experimental plots of _B. tenella_ were also found to continually infect local larval populations of cockchafer across a four-year study in France [63]. Even in the absence of epizootics, there is considerable evidence that _Beauveria_ can persists in the soil long-term, depending on formulation type, applicationstrategy, soil type, and field management [112; 113; 114; 115] and may become infectious under the right abiotic conditions [116].