Effects of plant latex based anti-termite formulations on Indian white termite Odontotermes obesus (Isoptera: Odontotermitidae) in sub-tropical high infestation areas

In the present investigation various bioassays were conducted to evaluate the anti-termite efficacy of plant latex based formulations to control population of Indian white termite in subtropical soil. Results reveal that crude latex, its fractions and combinatorial fractions have shown very high toxicity against O. obesus. The LD50 values for different latex fractions of 24 h were in a range of 5.0 17.613 μg/mg while combined mixtures of Calotropis procera have shown synergistic activity against termites and caused comparably high mortality with LD50 1.987 6.016 μg/mg. The mortality rate was found dose and time dependent as it was found to be increased with an increase in dose and exposure period. In olfactometry tests, C. procera latex solvent fractions have shown significant repellency at a very low dose 0.010 0.320 μg/mg. Interestingly, solvent fractions have significantly repelled large numbers of worker termites due to volatile action of active components of latex and different additives. ED50 values obtained in crude latex were 0.121 μg/mg body weights while combinatorial formulations have shown ED50 in between 0.015 0.036 μg/mg. Statistical analysis of repelled and un-repelled termites gave a low Chi-square value (X value = 0.890) which is an indicator of independence of repellent action in randomly selected termite groups. In field experiments pre-soaked cotton threads impregnated with Calotropis procera crude latex were tagged around tree trunks of Tectona grandis provided a wider protection against O. obesus. By employing these pre-coated threads, termite infestation and tunneling activity were significantly decreased (p < 0.05 and 0.01). When germinating crop plants were sprayed with various plant latex formulations, these have caused very high protective efficacy against termite infestation. It has significantly reduced crop losses up to 6.45%. There was a significant difference in infestation obtained in control and treatment groups (P < 0.05 and 0.01) which shows that Calotropis procera possesses enough anti-termite potential against Indian white termite, O. obesus population. If used these, formulations may also provide wide a range of control against other kinds of pests including house hold, medical and veterinary. However, Calotropis procera latex based formulations can be recommended for effective control of termites in high infestation areas by applying spray, or in form of poison baits or as fumigant in pure form.