A Review of Biopesticides and Their Mode of Action Against Insect Pests - Environmental Sustainability: Role of Green Technologies - page 50

pesticides need to be continuously supervised to
ensure that they do not become capable of injur-
ing nontarget organisms, including humans
(Mazid et al. 2011 ). In previous studies, the
microbial pesticide advance has resulted in a sig-
nifi cant decrease of synthetic chemical insecti-
cide usage (James 2009 ).
Gray et al. ( 2006 ) reported Bt toxins produced
by plant growth-promoting rhizobacteria, which
also develop bacteriocin compounds of insecti-
cidal attributes. Bt is marketed worldwide for the
control of different important plant pests, mainly
caterpillars, mosquito larvae, and black fl ies.
Commercial Bt -based products include powders
containing a combination of dried spores and
crystal toxins. They are applied on leaves or other
environments where the insect larvae feed. Toxin
genes from Bt have been genetically engineered
into several crops.

was termed M. anisopliae by Sorokin in 1883
(Tulloch 1976 ).
Several entomopathogenic fungi and their
derivatives are also used as microbial pesticides. M.
anisopliae are hyphomycete entomopathogenic
fungi most widely used for insect pest control and
are ubiquitous worldwide. This species comprises
a huge number of different strains and isolates of
various geographical origins and from different
types of hosts (Roberts and St. Leger 2004 ).
Under natural conditions, Metarhizium are
found in the soil, where the moist conditions per-
mit fi lamentous growth and production of infec-
tious spores, called conidia, which infect
soil-dwelling insects upon contact (Fig. 2 ). M.
anisopliae has the potential to be used as a bio-
control agent, particularly for malaria vector spe-
cies, and is also a suitable candidate for further
research and development (Mnyone et al. 2010 ).
Driver et al. ( 2000 ) reevaluated the taxonomy of
the genus Metarhizium using sequence data from
ITS and 28S rDNA D3 regions and also using
RAPD patterns, revealing ten distinguishable
clades. M. anisopliae var. anisopliae represents
clade 9. These entomopathogenic fungi have been
viewed as safe and regarded as an environmentally
satisfactory alternative to synthetic chemical pesti-
cides (Domsch et al. 1980 ; Zimmermann 1993 ).
Recently, these entomopathogenic fungi have been
registered as microbial agents and are also under
commercial development for the biological control
of several pests (Butt et al. 2001a , b ).

3 Fungi

3.1 Metarhizium anisopliae

M. anisopliae Sorokin var. anisopliae is an
essential entomopathogenic fungus. It propa-
gates worldwide in the soil, demonstrating a
wide range of insect host species. This subspe-
cies was fi rst described in 1879 by Metschnikoff,
under the term Entomophthora anisopliae , as a
pathogen of the wheat cockchafer, and later it

Fig. 2 Mode of action of entomopathogenic fungi against lepidopteran insects