BACTERIA.Wolbachiaspp. have been detected
in a population of Neoseiulus barkeri
(Hughes) collected in The Netherlands and a
population of Neoseiulus bibens Blommers
from Madagascar (Breeuwer and Jacobs,
1996). Effects of Wolbachia spp. on these
mites have not yet been investigated, but it is
likely that Wolbachia are associated with non-
reciprocal reproductive incompatibilities (for
a discussion, see Breeuwer and Jacobs, 1996).
PROTOZOA.In 1991, microsporidia were
reported in Amblyseius cucumeris and
Amyblyseius barkeri, predatory mites that are
used for controlling western flower thrips
(Frankliniella occidentalis (Pergande)) and
onion thrips (Thrips tabaci (Lindeman)),
respectively (Beerling and van der Geest,
1991). This was the first report of
microsporidia in mass-reared predatory
mites. Microsporidia reduce the fecundity of
A. cucumerisand A. barkeriand lower their
predation capacity (Ramakers et al., 1989;
Beerling and van der Geest, 1991). During
advanced stages of the disease, infected
mites are swollen, white and lethargic and
spores are so numerous that they often con-
ceal the internal tissues (Beerling and van
der Geest, 1991). Microsporidia may be
transmitted vertically (from parent to prog-
eny) or horizontally (from one infected indi-
vidual to another) (Beerling and van der
Geest, 1991). However, the mechanisms of
pathogen transmission have not been deter-
mined for this system. Three types of
microsporidian spores have been found in
A. cucumerisand A. barkeri(Beerling et al.,
1993) but it is unclear if these represent one
species of microsporidia with three different
spore types or three distinct species.
Beerling et al.(1993) developed a mono-
clonal-antibody ELISA as a bioassay for the
detection of microsporidia in mass-reared A.
cucumerisand A. barkeri. Further work is
needed to determine the sensitivity of this
test as a suitable screening method for
microsporidia in mites.
FUNGI.A pathogenic fungus has been
reported from phytoseiid mites collected in
Brazil (Furtado et al., 1996; Keller, 1997).
Field-collected Euseius citrifolius (formerly
Amblyseius citrifolius) (Denmark and Muma)
were heavily infected by the fungus
Neozygites sp. (Furtado et al., 1996) and
showed a high rate of mortality. Some cadav-
ers carried near-white hyphae that produced
pear-shaped conidia. However, Amblyseius
idaeusDenmark and Muma and Amblyseius
limonicusGarman and McGregor were not
infected by Neozygites sp. isolated from the
cassava green mite in laboratory tests (De
Moraes and Delalibera, 1992). E. citrifolius
collected in Brazil on two subsequent occa-
sions contained viable resting spores and
hyphal bodies of two distinct fungal species
identified as Neozygites acaricida and
Neozygites cf. acaridis(Keller, 1997).UNIDENTIFIED DISEASE.In some cases, Amblyseius
hibisci (Chant) exhibit dark-red occlusions
within the alimentary tract near the distal
opisthosoma. These are thought to be associ-
ated with the incomplete digestion of their
prey, the citrus red mite (Panonychus citri
(McGregor)). Symptomatic mites appear dor-
sal–ventrally flattened and are lethargic;
females do not produce eggs and complete
mortality of immatures occurs at 32 and
35°C. Symptoms are not observed in mites
fed a diet of pollen from the ice plant,
Malephora crocea(Jacq.) (Tanigoshi et al., 1981).Phytoseiulus: predators of mites
VIRUSES.Gravid Phytoseiulus persimilisAthias-
Henriot females may carry unidentified,
non-occluded virus-like particles in the yolk
of developing eggs. The effects of these
virus-like particles on predator efficacy are
not known (Bjørnson et al., 1997). Mites
infected with Rickettsiella phytoseiulicontain
virus-like particles that are abundant and
visible in the dorsal part of the body, imme-
diately below the cuticle (Sut’áková andˇ
Rüttgen, 1978).BACTERIA.R. phytoseiulireported in P. persim-
ilis from the Ukraine (Sut’áková and Rüttgen, ̆
1978) are observed throughout the tissues,
with the exception of the gut diverticula,
salivary glands and Malpighian tubules. R.
phytoseiulihas no known effect on the devel-
opment and longevity of P. persimilis.Pathogens of Natural Enemies and Pollinators 141