[Edited_by_A._Ciancio,_C.N.R.,_Bari,_Italy_and_K.(Bookos.org)

MITE PATHOGENS IN IPM
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Figure 11. Cross section of a microsporidian spore and a crystal of Phytoseiulus
persimilis. The polar filament of the spore is not visible. Photograph by Dr. Susan
Bjørnson.
Poor performance of the predators, due to the presence of pathogens in the mass
cultures is a threat to integrated pest management in especially glasshouse crops
(e.g. Steiner, 1993). It is clear that more attention should be paid to a good
monitoring system. The presence of pathogens should be established early in the
manufacturing process, which requires a fast and reliable detection method. In the
past, visual inspection with the aid of a binocular or compound microscope was the
only way to establish the presence of these pathogens. A polarizing filter is needed
to avoid confusion with the birefringent crystals that are commonly present inside
adult phytoseiids (see Section 6.1).
The availability of a method to detect the disease at an early stage is of great
importance for the commercial production of natural enemies. Beerling et al. (1993)
developed an ELISA to detect the presence of microsporidiosis in predator massrearings.
Monoclonal antibodies were produced against one spore type (oblong), that
was present in both prey and predator species. A next step would be the use of more
sensitive molecular techniques which makes the detection of microsporidiosis
possible regardless of spore type, and even before spores are formed (Malone &
McIvor, 1996).
Recently, a new species of microsporidia was described by Becnel, Jeyaprakash,
Hoy, and Shapiro (2002) from the predatory mite Metaseiulus occidentalis. Mites
infected with Oligosporidium occidentalis do not show any external or gross signs
of infection, but electronmicroscopical analysis reveales that the pathogen develops
in eggs, larvae, nymphs and adults of the predator. Mature cells of O. occidentalis can
be found in cecal cells, lyrate organ cells, ganglia, epithelial cells, muscle, inside the
ovary and in developing and mature eggs. Female predators have in general a shorter