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Abstract:
Toxorhynchites spp. mosquitoes are recognised as potential
biological control agents of pest and vector species of mosquito.
There have been many attempts to use them for this purpose since
the beginning of the twentieth century, although with relatively
low levels of success, which has been attributed to a lack of
knowledge of the general biology of Toxorhynchites mosquitos.
Increasing resistance of vector mosquitoes to traditional chemical
pesticides and the expansion of the ranges of these vector mosquitoes
have made the search for alternative methods of mosquito control
imperative. This review draws together the current knowledge
of both the taxonomy and the general biology of Toxorhynchites
mosquitoes and details previous attempts to use this group as
biocontrol agents and in integrated control programmes. In addition,
it makes recommendations for further study of this group in
order to facilitate their successful utilization against vector
mosquitoes.
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Abstract:
A database of nontarget effects in classical and inundative
biocontrol (of insects) was constructed based on various published
and unpublished sources. Data were found relating to the nontarget
effects in only 1.7% of all documented classical biocontrol
introductions. Eighty-seven classical introductions have led
to recorded nontarget effects, but most of these were minor.
Seventeen of these introductions led to population reductions
or effects of similar severity. Only one purported extinction
was found, and even here the level of supporting evidence is
low. While the direct evidence is thus almost non-existent,
the impression from the available data is that there may have
been many more nontarget effects, particularly in the very early
history of classical biocontrol (especially in Hawaii), and
that some of the polyphagous insect predators and parasitoids
that are still now occasionally being used have significant
community level impacts. In the latter cases, these introductions
may usually have been justified in cost-benefit terms, or by
socio-economic urgency, but this is not always clear.
Safety in inundative biocontrol is apparently justified not
by the host range of the agents (often considerable), or even
the population effects in the field on nontargets (which occur
as many times as not), but by the transience of effects, lack
of persistence, and the argument that agents, if not already
present, are unlikely to establish. The ecological underpinning
of these conclusions requires continuing investigation, so that
we can be more sure about the safety of these agents under various
use strategies.
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