Bioefficacy of some insect growth regulators and plant extracts against mosquito larvae of Aedes aegypti

Susceptibility levels of Aedes aegypti mosquito larvae, collected from Al-Taif governorate, Saudi Arabia were evaluated against three insect growth regulators (IGRs) Diflox flowable, Baycidal and Sumilarv as well as three plant extracts Thevetia nerviifolia, Plumeria acuifolia and Lantana camara. According to values of IC₅₀ (concentration which to inhibit the emergence of 50% of adults), the IGR Diflox flowable (0.0028 ppm) proved to be more effective against mosquito larvae of A. aegypti than Baycidal (0.0033 ppm) and Sumilarv (0.047 ppm) by about 1.8 and 16.8 times, respectively. The change in the susceptibility level of the present mosquito larvae may be attributed to the differential mode of actions of the tested IGRs and its effective concentrations. On the other hand, the plant extract T. neriifolia proved to be more effective against A. aegypti larvae, followed by P. acuifolia and L. camara by about 1.3 and 3.7 folds, respectively. This was highly pronounced on the basis of IC₅₀ values obtained which were in respect 85.5 ppm, 108.7 ppm and 317.4 ppm. Variation in the susceptibility status of A. aegypt larvae is possibly due to differences in the nature of active components present in the test plant extracts and its effective concentrations. Generally, the tested IGRs and plant extracts exhibited promising larvicidal activity and can be used as alternatives for mosquito control.