Effect of insect growth regulators on hatching of eggs of three vector mosquito species
Hatchability of eggs ofCulex quinquefasciatus, Aedes aegypti andAnopheles stephensi was studied by exposing freshly laid (0–1 h) and older (12–18 h) eggs to varying concentrations (0–0001–l-0mg/l) of 6 insect growth regulators viz. OMS 3019, OMS 3007, OMS 2015, OMS 3031, OMS 3013 and OMS 3009. In all the 3 species, dosage dependent response was observed. The response was also dependent on the age of eggs. Among the 6 IGR compounds OMS 3031 was found highly active resulting in maximum reduction in hatching of freshly laid eggs ofAnopheles stephensi (99-95%) followed byAedes aegypti (89–9%) whereas 50% inhibition in hatching occurred in older eggs ofCulex quinquefasciatus exposed to OMS 3009 at the same dosage. Dose, age and dose and age dependent hatching was evident in eggs of the 3 test species exposed to insect growth regulators OMS 3019, OMS 3013 and OMS 2015. Higher proportion of unhatched eggs with varying abnormalities was noticed in test species. Percentage mortality observed was higher in first instar larvae hatched from treated eggs reared in untreated water. Therefore, insect growth regulators have great potency in suppressing the population by affecting hatching of mosquito eggs in addition to inhibition of adult emergence, thus providing a useful tool for integrated vector management.