A Review of Biopesticides and Their Mode of Action Against Insect Pests - Environmental Sustainability: Role of Green Technologies - page 51

M. anisopliae strains are obtained from different
geographical localities (Fegan et al. 1993 ), as sug-
gested, among others, by extremely variable toxici-
ties (Goettel and Jaronski 1997 ). M. anisopliae have
been used on a large scale in countries like Brazil,
where 100,000 ha of sugarcanes are treated every
year (Faria and Magalhães 2001 ). They are released
in the fi eld after thorough assessment of strains.
Consorting to Goettel et al. ( 2001 ) have reported
that the growth and application of fungi as micro-
bial agents for biocontrol of insect pest involve tests
with mammalian models to evaluate possible
human and animal health risks.

(Moscardi 1999 ). Even so, the application of
baculoviruses is still limited in the fi eld of agricul-
ture and horticulture where the thresholds for pest
damage tend to be minimized. In Lepidoptera, i.e.,
the primary group where baculoviruses have been
isolated, they only cause mortality in the larval
stage (Cory 2000 ).
Baculoviruses need to be ingested by the lar-
vae to initiate infection. After ingestion, they
enter the insect's body through the midgut and
from there they spread throughout the body,
although in some insects, infection can be limited
to the insect midgut or the fat body (Fig. 3 ). Two
groups of baculoviruses exist: the nucleopoly-
hedroviruses (NPVs) and granuloviruses (GVs).
In NPVs, occlusion bodies comprise numerous
virus particles, but in GVs, occlusion bodies
ordinarily contain just one virus particle. A
common feature of baculoviruses is that they are
occluded, i.e., the virus particles are embedded
in a protein matrix. The presence of occlusion
bodies plays an essential role in baculovirus
biology as it allows the virus to survive outside
the host (Cory 2000 ).

4 Virus

4.1 Baculovirus

Baculoviruses are double-stranded DNA viruses
present in arthropods, mainly insects. Baculoviruses
are usually highly pathogenic and have been used
effi caciously in their natural form as biocontrol
agents against numerous serious insect pests

Fig. 3 Mode of action of baculoviruses against lepidopteran insects