Comparative Bioefficacy of Indigenous Phytoextracts against Subterranean Termites Odontotermes obesus Ramb. (Isoptera: Termitidae)

Methanolic extracts and essential oils of ten indigenous plant species were evaluated for their insecticidal and repellency potential against the subterranean termite Odontotermes obesus Ramb, a destructive insect pest of wooden infrastructures, agricultural crops, orchards and forest plantations. Standard filter paper disc method was used for both toxicity and repellency bioassays according to completely randomized design. The response of termite workers varied with plant species, botanical concentration and exposure time. The extracts of Azadirachta indica (neem) and Nerium indicum (oleander) appeared to be most effective against the termites with minimum LC50 (6.35 and 10.38%, respectively) and LT50 (12.11 and 17.49 h, respectively) values, followed by the extract of Gardenia jasminoides (gardenia). While the extracts of N. indicum (oleander) and Dodonaea viscosa (sanatha) exhibited maximum repellency (up to 78%) of termite individuals, followed by A. indica (neem). In addition, the essential oils of Citrus aurantium (sour orange) and Cymbopogon citratus (lemon grass) were most effective against O. obesus termites with minimum LC50 (0.44 and 0.74%, respectively) and LT50 (10.91 and 16.89 h, respectively) values, followed by Allium sativum (garlic). While Syzygium aromaticum (clovebud) and A. sativum oils exhibited maximum repellency (up to 75%) of the termite individuals, followed by C. aurantium. These findings corroborate the effectiveness of indigenous plant extracts and essential oils as safe and environment-friendly alternates to hazardous synthetic insecticides, and suggest the incorporation of these phytoextracts in the future pest management programs against subterranean termites and other insect pests.