Chalkbrood is a disease of bee larvae caused by fungi in the genus Ascosphaera. The alfalfa leafcutting bee (Megachile rotundata) is managed for alfalfa seed production. Chalkbrood is a serious mortality factor in the managed bees, especially in the U. S. A. aggregata is thought to be the main species causing these infections, but at least nine other species occur in megachilids, and we have frequently seen them in M. rotundata populations. Spores are usually required for morphological identification of these fungi, but some of the Ascosphaera (including A. aggregata) do not complete development on artificial media. Therefore, when using morphological methods for identification, sporulating cadavers are necessary for species identification. We have developed a PCR marker that allows us to identify the presence of any of Ascosphaera, regardless of whether symptoms or spores are yet apparent in a host. We are then able to identify the pathogen to species using cleaved amplified polymorphic sequences (CAPS), a restriction analysis. These methods will allow us sample large numbers of bee larvae for infections, without having to culture the fungi, and with more reliability than morphological examinations.
Species 1: Hymenoptera Megachilidae Megachile rotundata (alfalfa leafcutting bee)
Species 2: Ascosphaerales Ascosphaeraceae Ascosphaera aggregata (chalkbrood)
Keywords: restriction analysis, PCR
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