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

the surface and space contaminated with any kind of bioactive substance are more limited, and the risk of undesired side effects on non-target organisms including vertebrates, as well as on the users and the public can be minimised. In the present investigations, novel slow-release granule formulations of BTI and methoprene were used to assess their residual efficacy against larvae of some susceptible mosquito and fly species. Our results confirmed a number of previous other studies of the excellent activity of BTI against Aedes larvae (Becker and Margalith 1993). BTI is nowadays the most selective and safe bioactive agent recommended for aedine mosquito control. A proper formulation, like Culigel granules, can extend its efficacy for a prolonged period. In the present laboratory experiments the BTI B 5 GR preparation proved to be effective for 4 weeks already at a concentration as low as 5 ppm (a. i.). The BIOPREN BM 5 GR formulation containing methoprene juvenoid, a hormonally active compound, provided a similar extended efficacy in a series of tests carried out both on mosquito and fly larvae. This JH analogue was among the first IGR-type chemicals which exhibited promising activity in the field when tested against mosquito larvae (Schaefer and Wilder 1972, 1973) or in surface treatments as a potential fly larvicide (Wright 1972, Wright et al. 1973). In our studies performed with larvae of sensitive Aedes species (Ae. aegypti and Ae. cantans), the BIOPREN BM 5 GR formulation, when used at 10 ppm (a. i.) in the laboratory or under simulated field conditions, prevented adult emergence for as long as 12 to 16 weeks. It should be noted, however, that under special conditions, such as those prevailing in closed containers (Fig. 5) the persistence of methoprene was reduced as a possible consequence of the relatively high temperature of the medium and the presence of bacteria, both favouring its fast decomposition. Irrespective of the fact that Musca domestica is a species of moderate sensitivity towards methoprene among manure-breeding flies, the present studies revealed that this compound, in a good formulation such as BIOPREN BM 5 GR, could produce high rates of residual efficacy for a long period in the laboratory. In addition, in a trial imitating the conditions of practical fly control it also proved suitably effective and suppressed extensive adult populations for several weeks. In conclusion it seems reasonable to summarise the main advantageous features of the new granule formulation used in these studies. This type of granule is constructed of an insoluble hydrophilic matrix, forming - after having swollen in water (or in a wet environment) - an activated gel, an ideal slow-release system. Culigel BD granules are not toxic and they were found to be (bio)degradable within a period of ca. 6 months. They can incorporate (encapsulate) diverse types of solid or liquid bioactive agents releasing them subsequently at timed, controlled rates, a fact that may significantly contribute to the prolonged residual activity of the active substance. This formulation protects active ingredient(s) against different undesired environmental effects (U V degradation, oxidation, hydrolysis, microbial attack etc.). As a consequence, the timing of treatment and the necessity of precise monitoring in mosquito control will be less critical, since these well-designed granules can be sprinkled onto larval breeding sites under more "comfortable" pre-flood conditions. The flotation characteristics being also essential in mosquito control (flotation near the surface or sinking in water), the stability of the active substance(s) and the "release profile" can be modified by addition of various inert components (stabilisers, dispersing agents, anti-dispersing agents, emulsifiers, surfactants, etc.). Another fact could be important in mosquito control is that the well-constructed granules, when