Field evaluation of lethal ovitraps for the control of dengue vectors in Lahore, Pakistan

Field evaluation of lethal ovitraps (LOs) containing various concentrations of Bacillus thuringiensis serovar israelensis (Bti), buprofezin (insect growth regulator) and integration of Bti + buprofezin (1:1) in water and 10% hay infusion against dengue vectors was carried out during August-October 2009, at two municipalities (Samanabad and Mughalpura) of Lahore, Punjab-Pakistan. Each municipality was divided in two blocks; control versus treatment block, with 18 randomly selected houses. Each block received 36 ovitraps/LOs with and without any treatment. In total 15 weekly collections, 10,152 Aedes aegypti eggs were recovered with 5,351 and 4,801 from treatment and control blocks, respectively, indicating that different treatments did not affect oviposition. However, hay infusion recovered more eggs (6,548) as compared to tap water (3,604). Ovitrap positive index (OPI) was higher in hay infusion as compared with tap water. Moreover, there was no significant difference in egg density index (EDI) in tap water compared with hay infusion. Effect of lethal ovitraps treated with different concentrations of Bti indicated that 100 and 10 ppm of this biocide completely inhibited pupal formation, as against 1 ppm where 41 and 60% pupae were formed in Samanabad and Mughalpura, respectively. LOs treated with buprofezin indicated that different concentrations of buprofezin were more effective in inhibiting the pupae-adults emergence as compared to Bti where lethal affect was more on larval stage. Integration of Bti + buprofezin in hay infusion was highly effective in reducing pupal formation and inhibiting adult emergence. There was complete inhibition of adult emergence at all concentrations (100-1 ppm) in integrated lethal ovitraps, indicating the most effective tool for controlling Aedes populations under natural conditions.