Termiticidal and Protozocidal Potentials of Thevetia peruviana Leaf Extract against Coptotermes heimi Wasmann (Blattodea; Rhinotermitidae)

Abstract

Coptotermes heimi wasmann is considered as a serious, invasive pest species of Southeast Asia causing huge economic losses annually. Wood is a complex mixture of cellulose, hemicellulose, and lignocellulose and thus acts as a complete source of food and nutrition for termites. Due to their feeding behavior termites damage everything that particularly comprises cellulose such as books, wooden structures, stored timber, buildings, living trees, forests, crops, and stored grain products. Coptotermes heimi even hollow out living trees, making them physically weaker and susceptible to falling under strong winds and harsh weather conditions. In our study, the leaf extract of Thevetia peruviana was investigated for its termiticidal, protozocidal, and anti tunneling properties against Coptotermes heimi. The dried powder of Thevetia peruviana leaves was extracted by ethanol with the help of the Soxhlet apparatus. Rapid termite mortality along with a reduction in gut protozoa was observed in a dose dependent manner after they were exposed to a leaf extract dose range of 5-20mg/ml for 14 days. Termite tunneling activity also decreased as the leaf extract concentration increased. After 2 weeks of exposure to the highest concentration (20mg/ml), termite mortality was observed at 94%, and a decrease of 58% was also observed in the gut protozoa population. Tunneling activity was restricted to 100% at the highest concentration. The LC50 value was calculated at 1.21mg/ml by using the concentration series data. The results of antifeedant indices exhibited that this plant has strong antifeedant activity at its highest concentration (A = 61.2). The results of GC-MS (gas chromatography coupled mass spectrometry) revealed the presence of glycosides (Thevetin A and B), benzoic acids, and long chain fatty acids. Collectively our results indicated that Thevetia peruviana is a highly poisonous plant possessing termiticidal and protozocidal properties and hence this plant would be a potential candidate for the development of plant-based insecticides for efficient termite control.