Another bit about Cape Bees also offers clues as to why varroa tends to be less of a problem in isolated colonies, or isolated apiaries:

> On the one hand, the severe extent of the "capensis calamity" (Allsopp and Crewe 1993) strongly suggests a high virulence of the invasive clonal lineage (Neumann and Moritz 2002; Dietemann et al. 2006, 2007). On the other hand, the low infestation levels in wild A. m. scutellata host populations (particularly in nature conservation reserves) indicate that natural transmission of the invasive A. m. capensis lineage is low (Hartel et al. 2006a) and primarily facilitated by apicultural activities (Moritz 2002; Neumann and Hepburn 2002; Dietemann et al. 2006). Hence, apicultural practice resulting in a particular high density of colonies in apiaries may be the basis for the dramatic calamities in apiaries but not in the wild (Moritz 2002).

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