Microflora associated with the alfalfa leafcutting bee, Megachile rotundata (Fab)(Hymenoptera: Megachilidae)in Saskatchewan, Canada

The microflora associated with Megachile rotundata was isolated from adult bees, lar-val cadavers, cell provisions, bee cell surfaces, and nest material. Dominant fungi included Alternar-ia alternata, Aspergillus niger, Eurotium chevalieri, Mucor sp, Penicillium spp, Saccharomyces sp, Trichoderma citrinoviride, and Trichosporonoides sp. Bacteria commonly isolated included Bacillus circulans, Bacillus mycoides, Enterobacter agglomerans, and Pseudomonas spp. These microorgan-isms may be involved in activities such as spoilage of provisions, production of enzymes, antibiotics, mycotoxins, and growth factors (vitamins, amino acids), metabolic conversion of provisions, and inhi-bition of competing microorganisms. Microbial succession was observed involving yeast and bacteri-al fermentation of provisions followed by mould overgrowth of cell contents; this process was often associated with larval mortality. The microflora isolated likely has a range of beneficial and deleteri-ous effects on M rotundata. Some fungal species reported here may also be potentially harmful to the health of leafcutting bee managers.