Susceptibility of Aedes aegypti L. to essential oils of Eryngium foetidum L. and Plectranthus amboinicus (Lour) Spreng

Abstract

Aedes aegypti is a major vector of yellow fever, dengue, and lymphatic filariasis. Increasing resistance to synthetic insecticides has necessitated the search for safer, plant-based alternatives. This study evaluated the susceptibility of adult female Aedes aegypti to the essential oils of Eryngium foetidum and Plectranthus amboinicus.

Methods:

Essential oils were extracted by hydrodistillation using a Clevenger apparatus. Susceptibility was assessed based on knockdown effects at concentrations of 6.25, 12.50, 25.00, 50.00, and 100.00 μl/ml. The negative control was 1 ml of 10% Tween 80, while deltamethrin served as the positive control. Each concentration and control was tested in quadruplicate, with 25 adult female mosquitoes per replicate (100 per concentration). Bioassays were conducted using Wheaton bottles coated with the respective test solutions.

Results:

Eryngium foetidum oil produced a concentration- and time-dependent knockdown effect, achieving 100% and 96% knockdown at 50.00 μl/ml and 100.00 μl/ml, respectively. Plectranthus amboinicus oil showed a non-linear concentration– response relationship. At 30 minutes, KD₅₀ values estimated by log-time probit analysis were 15.236 μl/ml for P. amboinicus and 59.311 μl/ml for E. foetidum, indicating greater susceptibility of Ae. aegypti to P. amboininicus oil. Only the positive control elicited knockdown among controls.

Conclusion:

Both essential oils demonstrated adulticidal activity, with P. amboinicus showing greater potency. These findings support further investigation of these plant-derived oils as potential eco-friendly mosquito control agents.