Potencijal horizontalnog prenosa piriproksifena u suzbijanju kućnog komarca (Culex pipiens biotip molestus) / The potential of horizontal distribution of pyriproxyfen in control of mosquitos Culex pipiens biotype molestus

Pyriproxyfen is an insect growth regulator which has a broad application in the control of mosquito number (Diptera: Culicidae). The recent studies emphasize the use of pyriproxyfen as a larvicide which is used in low concentrations (1ppb) with a great efficiacy on target organisms. The WHO supports its application as the concentrations which are sufficient for the inhibition of mosquito larvae development do not affect the quality of drinking water even when they are present in it. The species Culex pipiens biotype molestus is, with us, known as an ''ordinary mosquito''. This species is not predominant in our region but the synonim of its name as well as its molesting activity and its vector potential (virus of the Western Nile) point at the necessity of a greater attention to be paid to the species Cx. p. pipiens biotype molestus. The laboratory research work was performed at the Laboratory for Medical and Veterinary Entomology with the aim of obtaining the preliminary results of pyriproxyfen activity and effect on the Cx. p. pipiens species, biotype molestus. The larvae (III and IV stage) pupae and eggs were exposed to the activity of pyriproxyfen with the studied concentrations of pyriproxyfen of 0.0001 ppm, 0.001 ppm, 0.002 ppm,0.007 ppm, 0.01 ppm, 0.025 ppm, 0.05 ppm, 0.075 ppm, 0.1 ppm and 1.0 ppm. Mosquito females were used in the horizontal transfer of pyriproxyfen from the base where pyroxyfen was applied in the concentration of 1.0 ppm. During the studies the influence of pyriproxyfen on the fertility and fecundity of grown females was investigated. The study results show that pyroproxyfen concentrations of 0.0075 to 1.0 ppb have the best effect on mortality of mosquito larvae. The obtained results indicate that the concentrations lower than 0.0075 ppm can be used in mosquito control at lower larvae stages. By increasing the concentration of pyroproxyfen in water solution the number of eggs in an egg hatch was reduced. The concentration of 1ppm showed the best effect on the inhibition increase of larvae hatch for the species Cx.p.pipiens biotype molestus. The difference in the average number of hatched eggs of females which had pyriproxyfen on their tarsuses in the process of horizontal tranfer was determined. Based on those facts the results confirm the possibility and the potential of horizontal transfer of pyriproxyfen in the control of mosquitos Cx.p.pipiens biotype molestus. The results of the potential of pyroproxyfen horizontal transef in the control of mosquitos Cx.p,pipiens biotype molestus are preliminary but with the tendency of simple implementation in the programme of mosquito control in urban zones with the emphasis on the regions in which it is impossible to locate each acquatic recipient. By introducing such a mode of control the biological potential of mosquitos as molesters and vectors of various diseases would be reduced to a great extent. In this way the application of growth regulator i.e. the active substance pyriproxyfen directly affects the reduction of the number of treatments in comparison with the application of convetiional larvicides particularly at places where urban mosquitos apper and frequently, due to the favourable development conditions, several generations overlap.