Insect Control: Biological and Synthetic Agents - Index of

412 11: Entomopathogenic Fungi and their Role in Regulation of Insect Populations
In most temperate countries, greenhouses are the
only place where inundative biological control of
crops with entomophthoralean fungi could be
recommended at present. Preparations of P. neoaphidis
could be tested against aphids in greenhouses
and may, due to some horizontal transmission
effects afterwards, prove to have some advantages
over other biological control agents used, including
Lecanicillium lecanii. For some of the greenhouse
pest–pathogen systems mentioned in Section 11.7,
there could also be some prospects in inundation.
Whatever the environment, a most promising release
strategy could be a combination: an inundation
with some immediate effect but including a
significant inoculative effect.
11.6.1. Mass Production
The success of any commercial microbial control
agent depends largely on the ability to produce adequate
supplies of the agent to economically manage
the target pest or pests. Entomopathogenic fungi
produce different types of spores, depending on the
growth environment. Aerial conidia are produced on
the surface of cadavers, while blastospores, sometimes
referred to as ‘‘hyphal bodies’’ or protoplasts,
are produced in the host’s hemocoel. Consequently,
the fermentation medium and method will also dictate
the type of spore that will be obtained. In
submerged culture, primarily mycelia and blastospores
are produced while aerial conidia are produced
on the surface of liquid media or on solid substrates.
Efficient mass production methods are mostly
lacking for entomophthoralean fungi as is knowledge
on their formulation. Despite the development
of methods for mass producing several species, to
date, there are no commercialized products based
on entomophthoralean fungi. Due to the short-lived
nature of entomophthoralean conidia, attempts at
mass production have targeted primarily mycelia or
resting spores (Pell et al., 2001).
Many insect cadavers killed by fungi can be found
in the environment in a dehydrated state; often,
transfer of these cadavers to conditions of high humidity
results in massive conidiogenesis and spore
release (e.g., Tyrrell, 1988). This phenomenon has
spurred the development of ‘‘dried mycelia’’ as a
potential way of mass producing and using entomopathogenic
fungi (McCabe and Soper, 1985). Mycelia
are mass produced in deep fermentation, air
dried in the presence of a sugar desiccant protectant,
granulated, and stored dehydrated under low temperature.
Upon rehydration, the fungus sporulates
on the granule surface. This method is suitable both
for entomophthoralean and hyphomycetous fungi.
Despite some successful field demonstrations using
dried mycelia against several insect pests (e.g.,
Pereira and Roberts, 1991; Krueger et al., 1992;
Krueger and Roberts, 1997; Booth et al., 2000;
Shah et al., 2000), this method has not yet been
adopted commercially.
Some entomopathogenic fungi produce conidia or
resting spores in submerged culture. Examples are
resting spores of the entomophthoraleans, Conidiobolus
obscurus (Latgé, 1980) and E. maimaiga
(Kogan and Hajek, 2000), and conidia of the hyphomycetous
fungi Culicinomyces clavisporus (Cooper
and Sweeney, 1986) and M. anisopliae var. acridum
(Jenkins and Prior, 1993). Submerged conidia of
some species perform as well as aerially produced
ones (e.g., M. anisopliae var. acridum; Jenkins and
Thomas, 1996). For other species this is not so, e.g.,
submerged conidia of C. clavisporus performed
worse than aerial conidia (Cooper and Sweeney,
1986). To date, there are no commercialized products
based on conidia or resting spores produced in
submerged culture.
Most Hyphomycetes produce blastospores in
submerged culture, but for the most part, these are
thin walled and short lived, and with few exceptions,
are used primarily to produce starter batches
for use in inoculation of aerial culture (see Section
11.6.2). In some cases, blastospores are more virulent
than aerial conidia (e.g., Jackson et al., 1997;
Lacey et al., 1999), and several commercial products
consist of blastospores produced in submerged culture
(e.g., L. lecanii and P. fumosoroseus; see below).
Solid state fermentation is used for production of
aerial conidia of a number of commercially produced
Hyphomycetes (see below). The solid substrates can
be either nutritive, such as bran, cereals, or rice, or
nonnutritive, such as vermiculite, clay, or sponge.
Production of B. bassiana and M. anisopliae on rice
is widely practiced in South America (Alves et al.,
2003), Africa (Cherry et al., 1999), and China (Feng
et al., 1994).
More details on the production of entomopathogenic
fungi can be found in Bartlett and Jaronski
(1988), Jenkins and Goettel (1997), Jenkins et al.
(1998), and Wraight et al. (2001).
11.6.2. Commercialized Products
There are many commercial products available
worldwide, most based on fungi from six to seven
species from Hyphomycetes (Shah and Goettel,
1999; Copping, 2001; Wraight et al., 2001; Alves
et al., 2003). Hyphomycetes are very well suited for
commercialization due to their relatively wider host
ranges, ease of production, shelf life, persistence,
and ease of application.