Allium sativum (Liliales: Asparagales) essential oil - based combinations – a potential larvicide for Culex quinquefasciatus (Diptera: Culicidae)
2020
Mahanta, Sudarshana | Khanikor, Bulbuli | Sarma, Riju
The indiscriminate use of synthetic insecticides for the control of harmful mosquitoes has been fostering menaces like resistance development, toxic hazards to non-target organisms etc. Here, studies are made to prepare a synergistic mixture comprising of low concentration of essential oils of Allium sativum (bulbs), Ocimum sanctum (leaves), Citrus grandis (leaves and peels) against Culex quinquefasciatus larvae with anticipation that the synergistic composition may offer a new solution to tackle Culex population. Essential oils were extracted and tested individually against larval stage and their activities were compared with WHO recommended synthetic larvicides, Temephos. Thorough inspection showed that A. sativum oil possessed the highest larvicidal activity amongst the oil tested; hence it was kept as a common ingredient while preparing the binary combinations. The final combinations were prepared from the LC10 concentration of each candidate at 1:1 volume ratio and tested against the same stage of mosquito. Results revealed that the A. sativum plus O. sanctum oil mixture was the most effective larvicide. To understand the mode of action of the selected treatments, we investigated percent inhibition of Acetylcholinesterase (AChE) enzyme and activity of Glutathione-S-Transferase (GST) enzyme of exposed and unexposed laboratory reared larvae which were found significantly lower in exposed larvae than the untreated larvae. The best binary combination was finally applied against large mass of field-collected larvae providing semi field condition and 75–85% mortality of larvae was recorded. Therefore, it can be proposed that the binary combination of A. sativum and O. sanctum is a potential larvicidal candidate against C. quinquefasciatus.
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