Diseases of Beneficial Arthropods
Presented Following Host Systematics
Pathogens that infect field or laboratory popu-
lations of beneficial arthropods are presented
in the following sections. Unidentified dis-
eases and descriptions of (potential)
pathogens whose effects are not yet clear have
also been included. However, the side-effects
of entomopathogens used as microbial pesti-
cides on beneficial arthropods are not dis-
cussed (for a review, see Lipa and Smits, 1999).
Often, host specificity for a pathogen or group
of pathogens has not been studied in great
detail and the range of susceptible hosts is
unknown. Therefore, a pathogen of a particu-
lar natural enemy may have a broader host
range and be virulent towards members of the
same and related genera. As a result,
pathogens of natural enemies are presented
according to host genus.
Entomopathogenic nematodes (Nematoda:
Heterorhabditidae, Steinernematidae)Heterorhabditis, Steinernema: general
parasites of arthropodsSeveral pathogens reduce the effectiveness of
entomopathogenic nematodes. These patho-
gens attack either the nematode or its bacterial
symbionts (for a review, see Kaya et al., 1998).
VIRUSES.Lysogenic phages have been iso-
lated from Photorhabdus luminescens and
Xenorhabdus sp., bacterial symbionts of
entomopathogenic nematodes (cited by
Kaya et al., 1998). These phages lyse the
symbiotic bacteria and thereby reduce the
food supply for developing nematodes.
Phages may become problematic in nema-
tode mass-production systems if they
become established. Future research is
needed to find a means of detecting and
eliminating them (Kaya et al., 1998).
PROTOZOA.Pleistophora schulbergiand Nosema
mesniliinfect Steinernema carpocapsae(Weiser)
(cited by Kaya et al., 1998); however, the
effect of these microsporidia on the efficacy
of S. carpocapsaeis unknown. An undescribed
microsporidium isolated from Steinernema
glaserihas detrimental effects on its host that
range from slight damage to mortality,
depending on the severity of infection.
Furthermore, infective S. glaserijuveniles are
smaller and do not live as long as uninfected
ones (cited by Kaya et al., 1998).
Neoplectana glaseri(Steiner) infected with
an unidentified microsporidium produce
very few infective juveniles. The
microsporidium infects all stages of N. glaseri,
including the eggs and infective juveniles.
Microsporidian developmental stages and
spores are observed throughout the intestine
and reproductive system. The intestinal
lumen of infective juveniles is frequently
packed with spores. The effects of the
microsporidium on N. glaseriare dependent
upon the severity of infection and range from
partial or complete castration in both sexes to
reduced survival or mortality. The inadver-
tent introduction of microsporidia to mass
cultures of N. glaserican cause problems in
mass rearings (Poinar, 1988).FUNGI.Nematophagous fungi are common
in soil and can reduce steinernemid and het-
erorhabdid populations. Predatory fungi
trap their prey using specialized hyphae that
penetrate into the body of the nematode,
whereas endoparasitic fungi produce spores
that infect their hosts.
There are several species of trapping fungi
that successfully trap steinernemids and het-
erorhabdids, including Monacrosporium euder-
matum, Monacrosporium cionopagum,
Monacrosporium elipsosporum, Geniculifera pau-
cispora, Nematoctonus concurrens, Arthrobotrys
robusta, Arthrobotrys oligosporaand Dactylaria
sp. (cited by Kaya et al., 1998). In addition to
their presence in the soil, trapping fungi may
also be present on the insect integument,
where they serve to protect against nematode
infection. Trapping fungi may survive as
saprophytes, whereas endoparasitic fungi are
obligate parasites. Spores of endoparasitic
fungi attach to the nematode cuticle, germi-
nate and penetrate into the body cavity. An
example of an entomopathogenic fungus
known to infect nematodes under natural
conditions is Hirsutella rhossiliensis(cited by
Kaya et al., 1998).Pathogens of Natural Enemies and Pollinators 139