Oviposition attractancy of an infusion from a wood inhabiting fungus for vector mosquitoes.

ABSTRACT

BACKGROUND & OBJECTIVES: Review of literature indicates that none of the chemicals so far studied for oviposition attractancy was found to be promising for operational use. Efforts are being made to find an effective substance to corner a large number of ovipositing females to selective breeding sites for ease of control operation. This will reduce insecticidal consumption and will be cost-effective. This study is aimed to evaluate the oviposition attractancy of aqueous infusion from a wood inhabiting fungus (Polyporus spp.) for vector mosquitoes both in the laboratory and under field conditions. METHODS: An aqueous infusion (10%) was prepared by soaking 10 g of fungal powder in 100 ml of chlorine-free tap water. The mixture was shaken thoroughly and filtered through Whatman No. 1 filter paper. The filtered infusion was tested for oviposition attractancy against vector mosquitoes both in the laboratory and under field conditions. RESULTS: The laboratory study on the dose-effect relationship indicated that at an optimum concentration of 4 ppm, maximum attractancy was observed. Water treated with aqueous fungal infusion (AFI) at 4 ppm received significantly more egg rafts/eggs of vector mosquitoes than other substrates like rearing water, natural breeding water and tap water. Trials conducted in the field showed that mud pots treated with AFI placed in both indoor and outdoor locations received significantly more Aedes aegypti eggs than the control. Similarly, treated pots placed in paddy fields attracted significantly more gravid Anopheles subpictus for oviposition than untreated pots. In contrast, the number of egg rafts of Culex quinquefasciatus laid in AFI treated pots was significantly less than in the control ones owing to strong natural olfactory factors associated with the breeding habitat. INTERPRETATION & CONCLUSION: The results indicated that there is scope for developing a trap incorporating this oviposition attractant along with insect growth regulator(s) (IGR) for surveillance and/or control of Ae. aegypti and other vector mosquitoes breeding in paddy fields.