Pathogenicity of Beauveria bassiana (Balsamo) Vuillemin (Deuteromycotina : Hyphomycetes) against the Odontotermes obesus (Rambur) workers (Isoptera : Termitidae) under laboratory conditions

Abstract

Odontotermes obesus (Rambur) (Isoptera: Termitidae) is a common termite pest found in almost all crop plants in South East part of Rajasthan (India).It causes considerably economic losses in tropical and subtropical areas and occurrence of termites in the crop field has become a major threat to farmers. Presently, the control methods mostly swing towards chemical that has led to high cost, persistence and adverse effects to the environment. Presently, emphasis has been given on safer bio control agents like fungi, protozoans, bacteria and virus etc. that are environmental friendly. The present investigation is an attempt to control Odontotermes obesus (R) workers with pathogenic fungus Beauveria bassiana . The pathogenicity of Beauveria bassiana (Balsamo) was tested against the worker termite at four different concentrations (4.5 x 10⁸, 4.5 x 10⁷, 4.5 x 10⁶ and 4.5 x 10⁵ conidia/ml.). Complete population check was observed after 8 days of post inoculation at 4.5 x 10⁸ conidia / ml with LC₅₀ value of 8.67 X 10⁷ conidia / ml. under laboratory conditions. ANOVA further supported the significance of the result (F= 89.61; df=3 and 8, P < 0.05).  LT₅₀ and LT₉₀ for highest dose (4.5 x 10⁸ conidia / ml) were 2.55 days and 5.15 days respectively with inverse correlation with concentrations. Various developmental changes such as abnormal appendages, fragile body, shrunken body, body covered with fungal mycelium were also indicative of chitin inhibitory nature of fungus thus revealing two fold effect on the treated insects. Thus the result shows that mycoinsecticide Beauveria bassiana has a great potential to control the termite and reduce the burden of chemical insecticides on the environment.