Impact of Terminalia chebula Retz. against Aedes aegypti L. and non-target aquatic predatory insects

- GC-MS analysis of seed extracts of T. chebula identified nine chemical compounds with major peak area in the 1,2,3-Benzenetriol (pyrogallol).
- Survival, and cell organelles of fourth instar larvae of Ae. aegypti was affected after treatment with T. chebula.
- The toxicological evaluation proved less toxic to the predatory aquatic insects, Tx. splendens and A. bouvieri.

Aedes aegypti Linn is one of the most important mosquito species. The vectors are responsible for causing deadly diseases like dengue and dengue hemorrhagic fever. Several chemical pesticides used to control these dengue vectors caused severe toxic significances on human health and other non-target beneficial insects. Therefore the current investigation has been made to access the bio-efficacy of the crude seed extracts of T. chebula against the dengue vector Ae. aegypti. The GC-MS analysis of crude seed extracts of T. chebula identified nine chemical compounds with major peak area in the 1,2,3-Benzenetriol (61.96%), followed by Tridecanoic acid (09.55%). Ae. aegypti larvae showed dose dependent mortality rate was observed between the treatments. Prominent protection rate at greater concentrations of 100 ppm and moderate protection at 75 and 50 ppm was observed in the repellent assay. Lethal concentration (LC50 and LC90) of fourth instar larvae of Ae. aegypti was observed in 138 and 220 ppm concentration respectively. Similarly, the seed extracts showed 100% adulticidal activity at the concentration of 400 ppm at 30 min of exposure time. Phytochemicals present in the seed extracts of T. chebula significantly affects the major portions of the midgut tissues of Ae. aegypti at the concentration of 100 ppm. The toxicological evaluation of seed extracts also proved non-toxic towards the A. bouvieri and Tx. splendens aquatic predatory insects. Hence, the present result suggest that bio-rational plant derived T. chebula could be incorporated in the dengue vector control and have no adverse effects on non-target beneficial insects.

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