Field larvicidal and oviposition repellent efficacy of three essential oil formulations for the control of filaria vector mosquito Culex quinquefasciatus Say (Diptera: Culicidae): A kill and push concept

Biological control of larval mosquitoes is in great demand due to the development of resistance against synthetic insecticides, environmental toxicity and the inability to protect habitats from further oviposition. In the present study, three botanical essential oils (BEOs) – citronella, eucalyptus, and pine oils – were formulated for the assessment of larvicidal and oviposition repellent efficacies against Culex quinquefasciatus Say, the filaria vector. The GC–MS profiling of BEOs showed the presence of 16 – 19 compounds covering 87.7–93% of oil composition. The resistance status of Culex quinquefasciatus population was evaluated with temephos (LC₅₀ = 0.001 ppm, LC₉₀ = 0.01 ppm). Larval bioassay of emulsifiable concentrate (EC) formulations prepared from eucalyptus and pine oils showed promising efficacy (LC₅₀ = 22.7 and 23.2 ppm) and LC₉₀ (63.8 and 62.4 ppm) compared to citronella oil EC (LC₅₀ = 43.4 ppm and LC₉₀ = 199.0 ppm). The field trials of eucalyptus + pine (1:1 ratio) EC showed 100% larval mortality for 3 weeks at 300 ppm compared to 2 weeks of individual oils. Further, the oviposition attraction index (OAI) for ECs of eucalyptus, pine, and their combination showed complete protection of breeding habitats from oviposition at 1st week and ?0.9 to ?1.0 OAI at 2nd week with slight reduction to ?0.5 at 3rd week. Citronella EC provided shortest larvicidal and oviposition repellent efficacy under the field conditions. The promising mosquitocidal activities of EC formulations of eucalyptus and pine or their combination suggest them as potential biocontrol vector control candidates over citronella oil.