Insect Control: Biological and Synthetic Agents - Index of

A10 Addendum: Genetically Modified
Baculoviruses for Pest Insect Control
S G Kamita, K-D Kang, A B Inceoglu, and
B D Hammock, University of California, Davis, USA
ß 2010 Elsevier B.V. All Rights Reserved
In our original comprehensive review 5 years ago,
we extolled the virtues and cautioned against the
limitations of genetically modified (GM) baculoviruses
for use in pest insect control. At that time
we concluded that GM baculoviruses (1) show potency
that is comparable to traditional chemical
insecticides, (2) pose little or no risk to humans,
other nontarget species, and the environment, and
(3) can make a near-immediate positive impact on
sustainable pest insect control programs. Scientific
literature during the past 5 years continues to support
these conclusions. Our enthusiastic support of
GM baculoviruses as potent and safe biopesticides
that can complement or even synergize traditional
chemical insecticides and biocontrol strategies has
not changed. The field, however, has been slow to
embrace our enthusiasm. The high cost of regulatory
barriers for GM products coupled with the efficacy
and safety of major GM plants as well as new
generation insecticides for the control of key noctuid
pests makes near-term commercial development
of GM baculoviruses unlikely in the United States.
In addition, in some other countries, including ones
where there is a clear economic advantage of GM
baculoviruses, there is a general unease with the use
of GM products. A positive trend has been the
increased use of natural (i.e., wild type) baculoviruses
for augmented biocontrol. This expanded
use of natural baculoviruses may serve as a positive
step in the acceptance of GM baculovirus as green
or biopesticides.
During the past 5 years, several interesting and
insightful reviews covering historical and applied
aspects of biological control with insect viruses
and other microbials were published. Arif (2005),
Inceoglu et al. (2006), and Szewczyk et al. (2006)
review historical aspects and current developments
of natural insect viruses and GM baculovirus
for pest insect control. Summers (2006), a pioneer in
the development of GM baculoviruses for protein
expression, reviews how advances in the development
of baculoviruses as protein expression vectors
were key in the development of GM baculovirus
biopesticides. Hynes and Boyetchko (2006), Lord
(2005), Hajek et al. (2007), Whetstone and Hammock
(2007), and Rosell et al. (2008) review formulation
strategies and the relative importance of baculoviruses
(both natural and GM) with respect to other microbials
and the role of baculoviruses as delivery systems
of insecticidal agents. Gelernter (2007) and Kunimi
(2007) review the current status of the use of baculoviruses
and other microbials in Asia.
In our original review, the genetic modifications
of the baculovirus genome were categorized into
three major approaches (1) insertion of hormone
and enzyme genes, (2) insertion of insect-selective
toxin genes, and (3) genome modifications. When
multiple approaches were combined into a single
construct, the modifications resulted in at best a
roughly 60% improvement in the speed of kill relative
to the wild-type virus with reductions in feeding
damage of roughly 70% (comparison of GM baculovirus-
and mock-infected insects). During the past
5 years, various groups (see the following paragraphs)
continued with single and technologystacked
approaches with similar improvements in
efficacy. Although the efficacy of current GM baculoviruses
is sufficient under many crop protection
scenarios, we believe that further improvements
(e.g., by improving toxin folding and/or expression,
identifying alternative insect-selective toxins, modifying
the virus backbone, improving formulation)
can be generated, if necessary, by sustained efforts
by private and public sectors so that this technology
is more attractive for commercial agriculture.
During the past 5 years, Rajendra et al. (2006),
Jinn et al., (2006), and Choi et al. (2008) continued
to study improved insecticidal efficacy by expressing
lepidopteran-selective toxin genes under various promoters.
Shim et al. (2009) developed a ‘‘stacked’’
construct that targets the host at three levels: the
gut, nervous system, and systemic baculovirus infection.
Constructs designed to express cathepsin B-like
(Hong-Lian et al., 2008) and L-like (Li et al., 2008;
Sun et al., 2009) proteases have also been tested
in the laboratory and field. The cathepsin L-like