Environmental Engineering Reference
In-Depth Information
Recently, it has been substantially demonstrated
that baculoviruses are not infectious to vertebrates
and plants. Also within the insects, their host range
is restricted to the order from which they were iso-
lated. Genetic engineering of baculoviruses has so
far been restricted to isolates from Lepidoptera
(Kolodny-Hirsch et al.
1997
). Baculoviruses vary
in the number of hosts that they can infect; some
seem to be particular to one species and hence are
very unlikely to be a hazard when genetically mod-
ifi ed, whereas others infect a range of hosts (Barber
et al.
1993
; Richards et al.
1999
; Cory et al.
2000
).
The majority of new baculovirus recombi-
nants now employ insect-selective toxins.
Genetic modifi cation has been mostly carried
out on the alfalfa looper,
Autographa califor-
nica
NPV (AcNPV)-the virus for which most
molecular information is available, including
the complete DNA sequence, which permits
precise insertion of foreign genes. Recently, the
development of genetically modifi ed baculovi-
ruses has expanded to other strains of commer-
cial or regional interest (Popham et al.
1997
;
Cory
2000
).
Baculovirus-infected insect larvae have pri-
marily initiated a cascade of molecular and cel-
lular appendages fi nally the larva enters into the
death and the development of huge amounts of
polyhedral occlusion bodies comprising rod-
shaped virions (Miller
1997
). Lately, a naturally
occurring baculovirus (
Agrotis ipsilon
multiple
nucleopolyhedrovirus, family Baculoviridae,
AgipMNPV) was indicated to have hope as a
microbial insecticide for controlling
A. ipsilon
in
turf (Prater et al.
2006
).
Numerous viral formulations are available pri-
marily for the control of caterpillar pests. For
instance, Certis has recently registered Madex™,
an increased-potency codling moth granulosis
virus (GV) that also affects oriental fruit moth
(OFM). Certis also deals Cyd-X™, which also
contains the codling moth GV and which can be
an effi cient tool for codling moth management
( Arthurs and Lacey
2004
; Arthurs et al.
2005
).
Aside from Madex and Cyd-X, Certis markets
Gemstar™, which contains
Heliothis zea
NPV,
and Spod-X™, which contains beet armyworm
NPV. Gemstar is also registered for the control of
lepidopteran pests, like the cotton bollworm and
budworm, caterpillars that are mainly dangerous
insect pests of corn, soybean, and other vegeta-
bles (Arthurs et al.
2005
). Furthermore, Certis
has registered a celery looper (
Syngrapha fal-
cifera
) NPV and an alfalfa looper (
Autographa
californica
) NPV (EPA
2006
).
5
Nematodes
5.1
Steinernema
(Rhabditida)
One of the new hot products in biopesticide is
nematodes. Pest nematodes can be supervised
with cover crops, crop rotation, and internaliza-
tion of organic material into the soil (McSorely
1999
). In the early 1990s, various effective ento-
mopathogenic nematodes from two genera,
namely,
Steinernema
and
Heterorhabditis
(Nematoda: Rhabditida), were discovered and
established as a biocontrol agent against insects
(Copping and Menn
2000
).
Insect-parasitic nematodes may encroach
upon soil-dwelling stages of insects and kill them
within 48 h through the expulsion of pathogenic
bacteria. After the host dies, the infectious stages
of the nematodes become adults and a modern
generation of infective juveniles (IJs) develops
(Fig.
4
). Entomopathogenic nematodes are com-
monly available for plant protection from serious
insect pests and diseases, and also there have
been various efforts to biocontrol insect pest pop-
ulations in the fi eld by employing IJs via spray-
ing. Nevertheless, little is known about the ability
of indigenous nematodes to infl uence insect pest
populations (Peters
1996
).
In nematodes, the parasitic cycle is initiated
by the third-stage IJs. These nonfeeding juveniles
infest suitable insect host and enter through the
insect's natural body openings like the anus,
mouth, and spiracles (Grewal et al.
1997
). Once
they have entered inside the host, nematodes
infest the hemocoel and then release their symbi-
otic bacteria into the intestine. After that, the bac-
teria cause septicemia, killing the host within
24-48 h (Fig.
4
). The uptake of IJs is rapidly
manipulating by the bacteria and decomposed the
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