Activity of essential oil from Stemodia viscosa Roxb against immature stages of Anopheles stephensi Liston, Aedes aegypti L and Culex quinquefasciatus say (Diptera: Culicidae)

Mosquitoes are crucial vectors globally, particularly prevalent in tropical regions. They are considered especially hazardous compared to other disease vectors due to the severe detrimental impacts they cause. The purpose of the present study was to evaluate the efficacy of essential oil from Stemodia viscosa against Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus mosquitoes. Concentrations of 3.125-50 ppm were used to check the mosquitocidal activity. S. viscosa essential oil displayed 96-100% ovicidal mortality against the eggs of these three species at 50 ppm concentration within 24 h; it was comparable to that of temephos the positive control. Strong mosquitocidal activity was observed, with LC50 and LC90 values of 8. 8, 5.9, 5.1 ppm and 37.5, 33.7 and 25.7 ppm against larvae of Ae. aegypti, Cx. quinquefasciatus and An. stephensi mosquitoes, respectively, at 24 h. Essential oil showed the least activity against pupae of all three vector mosquitoes at 50 ppm concentration. Three major compounds-Caryophyllene (64.05%), Humulene (12.83%) and Androsta-1,4,6-triene-3,17-dione (10.31%)-were identified as the main compounds present in the essential oil which may account for these activities. Toxicity studies revealed that the essential oil from S. viscosa had no negative effects on tested natural predators. The essential oil was then formulated for field-level application and its toxicity was tested in laboratory setting. The results showed promising mosquitocidal activity without any toxicity toward the tested natural predators. These observations strongly indicate that the essential oil from S. viscosa can be used as mosquitocidal agent against three disease-transmitting mosquitoes without causing environmental damage, making it effective green mosquitocide.