Introduction to Fungi, Third Edition

ENTOMOPHTHORALES
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layered thickened walls. Such conidia have been
termed loriconidia (Gindin & Ben-Ze’ev, 1994).
No zygospores have been reported for C. coronatus,
structures resembling zygospores being interpreted
as aerial chlamydospores.
Conidiobolus coronatus is a parasite of aphids,
termites and whiteflies attacking tobacco, cotton
and sweet potato, as well as of waxmoths and
some other insects (Gindin & Ben-Ze’ev, 1994;
Bogus & Szczepanik, 2000). It should be regarded
as a relatively primitive opportunistic pathogen.
Infection of termites can occur by penetration of
germ tubes through the exoskeleton, or via the
oesophagus after ingestion of germinated conidia
(Yendol & Paschke, 1965). Following infection
of insects, death can occur within 2 days, probably
by the production of toxins (Evans, 1989).
A highly insecticidal 30 kDa protein has been
found in mycelium and culture filtrates of
C. coronatus (Bogus & Scheller, 2002). This and
possibly other toxins induce damage to blood
cells or early death in several insects when
injected into the haemocoel. In artificially
infected waxmoths (Galleria mellonella), infection
is followed by melanization of the host cuticle
and damage to the Malpighian tubules with
no evidence of tissue penetration (Bogus &
Szczepanik, 2000). Conidiobolus coronatus and
C. obscurus are being investigated as potential
agents of biological control of insect pests.
Conidiobolus coronatus is also pathogenic to
mammals such as horses, llama, chimpanzee
and man. Human infections are most common in
the moist tropics and subtropics, especially in
male outdoor workers from the rain forests of
West Africa. Although the mode of transmission
has not been established it is probably by inhalation
of spores which germinate in the nasal
mucosa. Other species of Conidiobolus known to
infect vertebrates are C. incongruus and C.
lamprauges. Isolates pathogenic to vertebrates
grow readily at 37°C (Gugnani, 1992; Ribes
et al., 2000).
7.5.3 Entomophthoraceae
Benny et al. (2001) included 12 entomopathogenic
genera in the family Entomophthoraceae
(Gr. ‘insect destroyer’), of which we shall study
the three most important, i.e. Erynia,
Entomophthora and Furia.
Erynia
There are about 12 species of Erynia parasitic
on terrestrial insects such as aphids and
Lepidoptera, but some attack the aquatic larval
stages of Diptera such as Simulium spp. (river
blackflies), stone flies and caddis flies.
Characteristic features of the genus are branched
conidiophores bearing uninucleate, bitunicate
primary conidia which are discharged by septal
eversion. Germination of primary conidia is by
the production of various types of secondary
conidia. Tertiary conidia may also develop.
Resting bodies (azygospores and zygospores)
occur in some, but not all species. Attempts are
being made to use Erynia neoaphidis to control
aphid populations in field crops (Pell et al., 2001).
Erynia neoaphidis
This species, synonymous with Entomophthora
aphidis, Pandora neoaphidis and Zoophthora neoaphidis,
is the most widespread aphid pathogen of
temperate regions and has been found on over
70 species of aphids on annual and perennial
crops. It also attacks aphids on non-cultivated
plants, a common example being the nettle
aphid, Microlophium (Fig. 7.40). Infected aphids
are cream to brown in colour. They are attached
on the ventral side to their plant host by fungal
rhizoids and their bodies are distended. Within
the body of an infected aphid there are numerous
closely packed, wide, septate hyphal bodies
(Fig. 7.41a). Widely spaced, thick-walled, long,
awl-shaped pseudocystidia (Fig. 7.41b) pierce
the cuticle and, surrounding them, numerous
tightly packed, branched conidiophores emerge,
usually made up of uninucleate segments
(Figs. 7.41b,d; Brobyn & Wilding, 1977). The tip
of the conidiophore is cut off by a two-ply
septum to form a uninucleate primary conidium
with a two-layered wall (Figs. 7.41d,e).
Under humid conditions (relative humidity
495%), primary conidia are discharged by
septal eversion for a distance of about 1 cm,
and detached conidia show a bulging papilla
at their base. Violent discharge projects the
conidia through the boundary layer of still air