No abstract

Difl ubezuron is increasingly used in areas where mosquito larvae developed resistance to other insecticides. In our community difl ubenzuron is not used to control mosquito larvae. Two formulations of 1% difl ubenzuron (on corn-cob EF-1, and zeolite EF-2) were tested on Culex pipiens L (larvae) on one canal in the Belgrade suburb area. The effect was followed for seven weeks after application of the formulations. Formulation EF1 achieved a reduction in mosquito L 1 L 2 larvae between 23.9% and 89.4%. Between the two used formulations there was no signifi cant difference in the number reduction of lower larval stages, but for the higher larval stages EF1 proved to be more effi cient.

In the territory of Belgrade, at 16 sites (15 of test and one control), which belong to different enviromental categories such as: parks (Topcider, Hajd park, park Banovo brdo, Sumice, Usce), park-forests (Kosutnjak, Zvezdara, SP Jajinci, Banjica, Ada Ciganlija) and forests (Avala, Lipovica, Bojcinska forest, Manastirska forest, Makis), there were investigated potential and actual risk of transmission of Borrelia burgdorferi sensu lato. Suplja Stena was taken as a control site, where no chemical treatment was performed. Once of month, from March to October 2012, ticks were collected by flag-hours (drag-and-drop) method. Ticks were determined by the species and all Ixodes ricinus were observed by a dark-field microscope. A total of 3,158 individual ticks were collected, out of which 2,797 (88,6%) were Ixodes ricinus, 175 (5,5%) Dermacentor reticulatus and 186 (5,9%) Rhipicephalus sanguineus. At forest sites there were collected 1,102 Ixodes ricinus, in park-forest regions 730 and in the parks 569. Infection rate of ticks by B. burgdorferi sensu lato at the forest sites ranged between 23,8 and 36,3%, in the park-forests region 23,2-32,6% and 23,8 to 40% in the parks. Twelve of the sites met the criteria for high potential risk and three of them for moderate risk. Except for Makis, at all the forest sites, the actual risk from March to April was certain, and in other months the risk varied. In the park-forest regions, the actual risk was registered 16 times, the possible risk 23 times, and the limited riosk once. At the sites belonging to the park areas, cetrain actual risk was established 3 times, possible risk 30 times and the limited 7 times At the control site Suplja Stena, the actual risk of transmission of B. burgdorferi sensu lato was registered during all the months of the reaserch. At the teritory of Belgrade there are favorable conditions for maintaining vector Lyme disease and the potential and actual risk of transmission of Borrelia burgdorferi sensu lato.

Culex mosquitos are important infectious diseases vectors in temperate and tropical regions of the World, affecting nearly 350 million people in both developed and developing countries. Our approach was to “recycle” the well-established larvicide, and by studying the tablets, pellets and granules as floating or sinking formulations, we found a method to optimise the use of diflubenzuron against Culex pipiens mosquitoes in field conditions. A standard WHO procedure was used to test the larvicide efficacy. The combined efficacy of all floating formulations was 10.7% higher than sinking preparations (p-value =0.002) and that maximised throughout the experiment on days 14 and 21, (p-values 0.012 and 0.008, respectively). All floating formulations kept their efficacies above 70% until day 21 of the experiment, while the mortality of sinking designs dropped significantly after day 14. The lowest efficacy was observed when sinking granules were used and the highest when floating tablets were applied in the canals. Only the floating tablets showed no significant changes in efficacy from day 1 to 21, but then that efficacy drops sharp until day 35. Since the larvae spend most of their time on the surface of the slow-moving waters to breathe, and floating pellets and tablets are made of materials that can serve as food sources, we conclude that these formulations have a higher efficacy, at least in conditions of non- or slow-moving waters. This study shows the importance of a systematic approach to reformulation of old, already proven and environmentally safe larvicides which can control the mosquito populations and their spreading of various pathogens.