APICULTURE AND SOCIAL INSECTS Susceptibility of Adult Aethina tumida (Coleoptera: Nitidulidae) to Entomopathogenic Fungi T. M. MUERRLE, 1 P. NEUMANN, 1, 2, 3 , J. F. DAMES, 4 H. R. HEPBURN, 1 AND M. P. HILL 1 J. Econ. Entomol. 99(1): 1Ð6 (2006) ABSTRACT Aethina tumida Murray (Coleoptera: Nitidulidae) is an invasive parasite species in populations of honey bees, Apis mellifera L. Aiming toward substitution of chemical control, we here identiÞed a naturally occurring fungal pathogen of adult A. tumida from its endemic range in South Africa [Metarhizium anisopliae (Metschnikoff) Sorokin variety anisopliae strain FI-203]. The suscep- tibility of adult beetles (n = 400) to this fungus and to three other generalist entomopathogenic fungal isolates [Metarhizium anisopliae, Beauveria bassiana (Balsamo) Vuillemin, and Hirsutella illustris Minter & Brady] was assessed using spore suspension bioassays. The data revealed signiÞcantly increased mortality in the B. bassiana (74.00  8.94%) and M. anisopliae variety anisopliae (28.00  16.43%) tests but not in the H. illustris (2.00  4.47%) and M. anisopliae (12.00  8.37%) groups. The results indicate a potential for entomopathogenic fungi as an alternative control of A. tumida. KEY WORDS Aethina tumida, Apis mellifera, biological control, entomopathogenic fungi Aethina tumida Murray (Coleoptera: Nitidulidae) is a parasite of honey bee, Apis mellifera L., colonies native to sub-Saharan Africa (Hepburn and Radloff 1998) and has recently become an invasive species (Hood 2004, Neumann and Elzen 2004). Although African honey bee subspecies are relatively tolerant A. tumida infestations, European-derived honey bees are con- siderable less tolerant (Hood 2004, Neumann and El- zen 2004). The rapid spread and high reproductive potential of A. tumida (Neumann et al. 2001, Muerrle and Neumann 2004), both within colonies as well as in stored hive products (Ellis et al. 2002, Ellis 2004), together with its capacity to hibernate in honey bee clusters makes it a potential worldwide pest of api- culture (Neumann and Elzen 2004). So far, control of A. tumida has focused on chemical treatments (Baxter et al. 1999a, b; Elzen et al. 1999), bearing the risks of both pest resistance and residues in the hive products (Neumann and Elzen 2004). Bi- ological control, using microbial pathogens and in par- ticular entomopathogenic fungi, has the potential as an alternative to chemical insecticides (Lacey et al. 2001). Indeed, fungal pathogens are often highly host- speciÞc and nontoxic to vertebrates (Lacey et al. 2001), suggesting that they also might constitute a feasible alternative control for A. tumida. A. tumida belongs to the coleopteran family Niti- dulidae with members mainly being phytophagous, fungivorous, or saprophytic on fermenting fruit or plant matter (Scholtz and Holm 1996). Some Nitidu- lidae are known to vector a variety of disease-causing microorganisms, for example, spores of Aspergillus fla- vus Link:Gray (Vega et al. 1995, Wicklow 1995). The fungivorous beetle Carpophilus freemani Dobson was shown to be able to transport conidia of Beauveria bassiana (Balsamo) Vuillemin via fecal material in laboratory tests, which makes it an efÞcient candidate as a natural vector of B. bassiana (Bruck and Lewis 2002). A. tumida was frequently reported to promote fermentation of honey within combs and may there- fore be a vector for fungal microorganisms (Lundie 1940, Schmolke 1974, Swart et al. 2001). A. tumida feed on fruit (Ellis et al. 2002) and decaying or fermenting hive products and reproduce readily on old and moldy combs (Muerrle and Neumann, unpublished data). These observations suggest that A. tumida may be tolerant to a variety of microbial pathogens, which naturally occur in their environment. However, Lun- die (1940) Þrst reported a potential unidentiÞed fun- gal control agent, when noticing high mortality of adult beetles during laboratory rearing. Similarly, Ellis et al. (2004), noted increased larval and pupal mortality of A. tumida and suggested that two ento- mopathogenic fungi, A. flavus or Aspergillus niger van Tieghem might be responsible. Mortality of adult A. tumida caused by an unidentiÞed fungus was also observed during beetle mass rearing (Muerrle and Neumann 2004) for experimental purposes (T.M.M. and P.N., unpublished data). The fungal genera Beauveria, Metarhizium, and Hirsutella are generalist entomopathogens with spe- 1 Department of Zoology and Entomology, Rhodes University, P.O. Box 94, Grahamstown 6140, South Africa. 2 Institut fu ¨ r Zoologie, Molekulare O ¨ kologie, Martin-Luther-Uni- versita ¨ t Halle-Wittenberg, Hoher Weg 4, D-06099 Halle (Saale), Ger- many. 3 Corresponding author, e-mail: p.neumann@zoologie.uni-halle.de. 4 Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, P.O. Box 94, Grahamstown 6140, South Africa. 0022-0493/06/0001Ð0006$04.00/0  2006 Entomological Society of America Downloaded from https://academic.oup.com/jee/article/99/1/1/2218301 by guest on 22 March 2022