Dr. Murai Éva - Gubányi András szerk.: Parasitologia Hungarica 29-30. (Budapest, 1997)

adults. The fact that mosquito and fly species often colonise vulnerable natural habitats or domestic and peridomestic environments, respectively, necessitates a new attitude as to their effective, more economical and target-oriented as well as environment-friendly control. New bioactive agents with safer toxicological profile should be developed and introduced into practice. In addition, their application should be focused on the breeding sites of larvae, thus reducing the total surface of treated and therefore contaminated area. This up-to-date approach provides a feasible and perspective alternative to current pest control operations based on traditional adulticides but, at the same time, promises even better efficacy achieved at acceptable costs. By the use of selectively acting biological (microbial) preparations and new compounds with a novel modes of action, the requirements of environment protection are satisfied to a great extent. Diverse types of bioactive agents against insects of medical or veterinary importance are available at present. In the market of so-called "biopesticides", entomopathogenic bacterial preparations, particularly those containing varieties of Bacillus thuringiensis, have occupied a major position. One serotype of these bacteria, B. thuringiensis subsp. israelensis (BTI) discovered 20 years ago (Goldberg and Margalith 1977), exhibits extremely good selectivity and efficacy against some Diptera, aedine and culicine mosquitoes being especially susceptible (Becker and Margalith 1993). Parasporal protein crystals of BTI have proven highly toxic after being ingested by mosquito larvae, via a series of specific biochemical reactions in the insect's gut (Adams et al. 1996). They are especially toxic to young larval stages, causing mortality in a relatively short time. Various commercial products, liquid and granular formulations of BTI are being used currently in mosquito control. Some preparations based on Insect Growth Regulators (IGRs) are also ideal mosquito and fly larvicides. According to the original description, IGRs are "compounds that alter specific growth and formative processes in insects" (Staal 1975,1982). These selective anti-insect agents kill insects by inducing irreversible, lethal derangement in growth and development, disrupting such essential processes as embryogenesis, moulting, metamorphosis, or reproduction. Their toxicity and environmental impact is generally low or negligible. IGRs are also characterised by some relatively narrow "physiological windows" of sensitivity in different developmental stages and by the more or less "slow" manifestation of their specific effects. One of the most common representatives of IGRs are juvenile hormone (JH) analogues often called juvenoids (Sehnal 1976, Henrick 1982, Wimmer and Romanuk 1989). These, in most cases, synthetic compounds mimic the multiple functions of natural JHs that regulate some critical processes in insect morphogenesis, reproduction and seasonal development. The selective mode of action and favourable toxicology have promoted their extensive research and subsequent commercial application. Some juvenoid preparations can be essential elements of IPM (Integrated Pest Management) technologies in agriculture, while others are recommended for use against harmful insects such as fleas, cockroaches, ants or termites. Manure breeding flies and some mosquitoes, predominantly flood-water species are also ideal target species. Methoprene, a compound with a simple aliphatic chemical structure, is the first juvenoid registered in the USA for mosquito control. It has also shown good efficacy in the suppression of extensive house fly populations by surface treatment of larval breeding medium or by oral (feed-through) application (Chamberlain 1975). Methoprene is a typical member of the group of chemicals considered as so-called "first-generation juvenoids" (Edwards 1993) that are characterised by high or moderate bioactivity, limited field stability, and some by notable volatility connected with very satisfying toxicological features.