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

MITE PATHOGENS IN IPM
285
central stem is normally slightly enlarged and is buried in sockets present in the epiand
procuticle.
The fungus apparently digests the lipoproteinaceous epicuticular layer that
attaches the base to the cuticular sockets. Subsequently, the process is followed by
additional chemical changes in the composition of the cuticle. Epidermal cells
display interesting pathological symptoms. In uninfected mites, epidermal cells form
a syncytium, but after infection a remarkable reaction occur in these cells. The cells
line up in almost a single row just below the outer limiting border of the epidermis.
Vacuoles appear in the cytoplasm of the epidermal cells, while organelles such as
mitochondria and Golgi apparatus are not anymore discernable.
In a search for control agents of the citrus red mites (CRM) in Israel, field
collected mite cadavers were examined for the presence of pathogens. This has
resulted in the finding of three species of fungi that were found to be associated with
mites. The fungi were described by Boekhout et al. (2003) as novel species
belonging to the Ustilagomycetes, a class that is also called the smut fungi. It is a
large taxon with over 1,400 species in 70 genera that are almost exclusively plant
pathogens. The three fungi are anamorphic (they have no sexual state) and belong
therefore to the Deuterymycetes. However, morphologically they are similar to
yeast-like fungi which have been classified in the Ustilaginales. Based on molecular
properties, they should be considered to belong to two different lineages within the
Exobasidiomycetidae of the Ustilaginomycetes (Basidiomycota). These fungi,
described as Meira geulakonigii, M. argovae and Acaromyces ingoldii, are hard to
isolate from field-collected material: they are slow-growing fungi and for their
identification physiological and molecular methods are needed. This probably
explains the fact that they have only recently been discovered.
The three fungi were further studied with respect to their potential as biological
control agents of phytophagous mites. Laboratory investigations showed that all
three fungi affected mites, although M. argovae showed no effect towards T. urticae.
(Gerson et al., 2008). Meira geulakonigii caused considerable mortality of spider
mites and citrus red mite. An interesting observation was that none of the fungi
invaded the mites, although the fungi did grow on the mite’s cadavers. It is assumed
that mortality among the mites was caused by the action of fungal toxins.
Further tests showed that the fungus was endophytically present within the
sealed grapefruit flowers and in the flavedo (the tough outer skin) of grapefruit.
There was no evidence that the fungus caused any damage to the plants, which led
the authors to the assumption that M. geulakonigii serves as a “body guard” of
grapefruits. Also, M. geulakonigii had only minimal fungicidal effect on some
predatory mites. This property, together with its tolerance to many insecticides and
acaricides, suggests that this fungus has possibilities for integrated control programs.
4.3. Ascomycota
The Ascomycota is a large taxon of fungi with approximately 2,000 genera and over
30,000 species. Members of the Ascomycota bear the sexual spores within an ascus,
originally a cell that at first contains a diploid nucleus resulting from karyogamy (the