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BNI September 2000 Vol 21. No. 4: Reviews

L.E. Collins and A. Blackwell

The biology of Toxorhynchites mosquitoes and and their potential as biocontrol agents. BNI 21 (4)


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.



L.D. Lynch and M.B. Thomas

Nontarget effects in the biocontrol of insects with insects, nematodes and microbial agents: the evidence. 


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of nontarget effects in classical and inundative biocontrol (of insects) was constructed based on various published and unpublished sources.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.