Efficacy of three formulations of diflubenzuron, an insect growth regulator, against Culex quinquefasciatus Say, the vector of Bancroftian filariasis in India

BACKGROUND & OBJECTIVES Insect growth regulators (IGRs) offer alternatives to conventional chemical larvicides that pose problem of resistance and environmental safety. However, only a limited number of IGRs have been approved for use in mosquito control. In the present study, two new formulations of the IGR diflubenzuron, 2 per cent granular (GR) and 2 per cent tablet (DT) were tested for its efficacy against Culex quinquefasciatus, in comparison to its 25 per cent wettable powder (WP) formulation. METHODS The WP, GR and DT formulations were tested in cesspits, street drains and abandoned wells each at four dosages, 25, 50, 75 and 100 g ai/ha. Additionally, the DT formulation was tested at a higher dosage of 1 tablet/m² (equal to 400 g ai/ha). RESULTS The WP and GR formulations yielded >80 per cent inhibition of adult emergence (IE) for 7-10 days in cesspits, 4-7 days in street drains and 7-21 days in abandoned wells at all dosages tested. The DT formulation was effective only at higher dosage 100 g ai/ha and or 1 tablet/m² for 7-15 days at all habitats. INTERPRETATION & CONCLUSIONS The trial showed that the dosage 25 g ai/ha of 25 per cent WP could be the field dosage for cesspits and wells, and 50 g ai/ha for drains, to be applied at weekly intervals. The dosages 25, 50 and 100 g ai/ha of 2 per cent GR could be the field dosages for application in cesspits at weekly intervals, in abandoned wells every three weeks and in drains at weekly intervals, respectively. Diflubenzuron 25 per cent WP and 2 per cent GR could be used for larval control of Cx. quinquefasciatus under integrated vector management programme.