INTEGRATED MOSQUITO MANAGEMENT IN DHAKA CITY: PROMISING NON-CHEMICAL COMPONENTS

Abstract:
Environmental alteration, habitat manipulation, introduction of predators appear as promising interventions for integrated mosquito management for Dhaka city. A survey of mosquito breeding grounds in 1994 showed 86.4% less larvae in drains with flowing water than stagnant drains, and 77.7% less in drains with guppy fish (Poecilia reticulata) than those without them. Lakes and ponds stocked with various fish species, had low average larval density (22 and 399/ m2) compared to others (3,140-23,421/m2). A 1996 survey of 2,456 larval habitats showed an average habitat index of 12.4, and on an average 10.7 larvae per positive habitat. Six fishes consumed on an average 10-700 larvae per individual in 24 hours; Clarias batrachus and Oreochromis niloticus consumed 2,180 and 398 larvae in only 2 hours. Among insects, 10 odonate nymphs consumed on an average 33 larvae and Naucoris, Nepa and Ranatra on an average 25 larvae in 24 hours. The vegetation cover in breeding grounds influenced larval population. A 25% cover with water hyacinth and duckweeds showed 62.7% less larvae in the former than the latter. Experiments with duckweeds showed a 40-100% reduction in oviposition due to duckweed cover. A decline in hatching, survival of immature stages, and adult emergence (1652%) compared to the controls (57-69%) was observed; in case of full cover no larvae survived beyond second instar. A 6 week programme of clearing drains, seeding with guppy and use of Malariol oil B gave control for 3 months.