Biology Reference
In-Depth Information
regard to their geographic distribution, host or prey specificity, or other biologi-
cal attributes. Will the released insects have unintended environmental effects?
In the case of short-term releases, can the released arthropods be recovered from
the release site? Assessments of fitness and host specificity are relatively easy
to assess in the laboratory, but evaluations of potential risks such as horizontal
transfer (HT) or unintended effects on ecosystem function are more difficult.
Risk issues associated with paratransgenesis appear similar to those of trans-
genic arthropods, except that the potential risk of HT could be greater due to
the relatively high rate of HT in the insect gut of transgenes into environmental
microorganisms taken in during feeding. Risk issues associated with the inser-
tion of a novel symbiont (such as
Wolbachia
) into a new host are perhaps lower,
although it is unknown how stable such infections will be in stressful natural
environments or how rapidly resistance to the effects of the symbiont could
develop in the host, which could result in the loss of efficacy.
Several steps are involved in a program designed to control pest arthropods
through genetic modifications, whether they be transgenesis, paratransgenesis,
RNAi, or insertion of a novel symbiont. First, the target species must be iden-
tified as a significant pest for which conventional control tactics are ineffec-
tive. Genetic manipulation is more expensive and time consuming than other
pest-management tactics. The increased costs are due, in part, because genetic
manipulations generate concerns about risk. The genetic engineer next will
want to ask, How best can our knowledge about the pest's physiology, ecol-
ogy, or behavior be used against it? How will the genetically modified strain be
deployed in a pest-management program?
If the ultimate deployment method requires mass rearing of very large num-
bers of high-quality insects, mass-rearing methods and release models must be
developed. The manipulated strain may be released into greenhouses or field
cages for evaluation of stability, fitness, and efficacy as a first step. Permission to
release a genetically modified arthropod will have to be obtained from (likely
several) regulatory agencies. Short-term releases may be made into small plots or
field cages. Currently, releases of genetically modified arthropods into the envi-
ronment in the United States must be short-term experiments, and the researcher
is expected to retrieve all released arthropods from the environment at the end
of the experiment (or the released arthropods should be sterile). At present
(2012), there are no guidelines in the United States regarding permanent releases
of genetically modified arthropods (GMAs). International efforts at regulation of
GMAs also remain limited; some nations have biosafety laws, but many do not.
Many pest-management programs, especially those involving
replacement
of pest
