• Special formulation and storage procedures are necessary for microbial
pesticides. Storage of microbial insecticides according to label directions is
mandatory to maintain the virulence of pathogens.
• Mass multiplication of natural enemies throughout the year is difficult thus limit
the availability in the market. The product registration process and less availability limit the use of biopesticides compared to chemical pesticides.
• Effectiveness of biopesticides is mainly depending upon the external environmental conditions such as temperature, relative humidity and rainfall. Weather
conditions should be suitable for the multiplication and survival of biocontrol
agents in the field.
11.5 Viruses as Biopesticides
Baculoviruses (BV) are widely used as viral biopesticides. They are highly pathogenic for insects and other arthropods. BV are tiny double-stranded DNA viruses
and parasitically replicating microscopic elements. The genus baculoviruses contain
three subgroups (1) nuclear polyhedrosis viruses (NPVs), (2) cytoplasmic polyhedrosis viruses (CPVs) and (3) granulosis viruses (GVs). They are considered as
inclusion viruses which differ in the number of occlusion body and structure of the
protective protein coat. NPV and CPV produce polyhedral bodies which are
comprised of numerous virus particles. GV produces granular occlusion bodies
which contain just one virus particle. The distinct mechanisms of NPV, CPV and
GV virus uncoating occur among the baculoviruses. NPVs uncoat within the
nucleus, CPVs uncoat in the cytoplasm and GVs uncoat within the nuclear pore
complex to establish infection in the host. The occlusion bodies help the virus to
survive outside the host (Cory 2000).
11.5.1 Mode of Action of Viruses
The mode of action of the viruses is like bacteria and needs to be ingested by
the insect larvae to initiate infection. Immediately after the ingestion, virus enters
the insect body through the intestinal epithelium and causes systemic infection in the
host cell. NPV passes through intestinal epithelium to hemocoel, fat body and other
tissue cells, disintegrates the integrity of the tissues and liquefies the cadavers. In
case of GV, the infection is limited to insect midgut (Fig. 11.2).
11.5.2 Steps Involved in the Preparation of NPV and CPV
Usually third to fourth-instar larvae of Helicoverpa armigera are infected with viral
food. The definitive phase of viral disease occurs over 5–10 days. Once the complete
infection of the virus in the larvae is completed, before death, putrefying infected
larvae climb higher in the plant canopy and start releasing billions of polyhedra which
aid in the dissemination of virus particles from the cadavers to the lower parts of the
11 Biopesticides for Pest Management
245
pesticides. Storage of microbial insecticides according to label directions is
mandatory to maintain the virulence of pathogens.
• Mass multiplication of natural enemies throughout the year is difficult thus limit
the availability in the market. The product registration process and less availability limit the use of biopesticides compared to chemical pesticides.
• Effectiveness of biopesticides is mainly depending upon the external environmental conditions such as temperature, relative humidity and rainfall. Weather
conditions should be suitable for the multiplication and survival of biocontrol
agents in the field.
11.5 Viruses as Biopesticides
Baculoviruses (BV) are widely used as viral biopesticides. They are highly pathogenic for insects and other arthropods. BV are tiny double-stranded DNA viruses
and parasitically replicating microscopic elements. The genus baculoviruses contain
three subgroups (1) nuclear polyhedrosis viruses (NPVs), (2) cytoplasmic polyhedrosis viruses (CPVs) and (3) granulosis viruses (GVs). They are considered as
inclusion viruses which differ in the number of occlusion body and structure of the
protective protein coat. NPV and CPV produce polyhedral bodies which are
comprised of numerous virus particles. GV produces granular occlusion bodies
which contain just one virus particle. The distinct mechanisms of NPV, CPV and
GV virus uncoating occur among the baculoviruses. NPVs uncoat within the
nucleus, CPVs uncoat in the cytoplasm and GVs uncoat within the nuclear pore
complex to establish infection in the host. The occlusion bodies help the virus to
survive outside the host (Cory 2000).
11.5.1 Mode of Action of Viruses
The mode of action of the viruses is like bacteria and needs to be ingested by
the insect larvae to initiate infection. Immediately after the ingestion, virus enters
the insect body through the intestinal epithelium and causes systemic infection in the
host cell. NPV passes through intestinal epithelium to hemocoel, fat body and other
tissue cells, disintegrates the integrity of the tissues and liquefies the cadavers. In
case of GV, the infection is limited to insect midgut (Fig. 11.2).
11.5.2 Steps Involved in the Preparation of NPV and CPV
Usually third to fourth-instar larvae of Helicoverpa armigera are infected with viral
food. The definitive phase of viral disease occurs over 5–10 days. Once the complete
infection of the virus in the larvae is completed, before death, putrefying infected
larvae climb higher in the plant canopy and start releasing billions of polyhedra which
aid in the dissemination of virus particles from the cadavers to the lower parts of the
11 Biopesticides for Pest Management
245