Insecticidal Activity of Extracts Derived from Different Parts of the Mangrove Tree Rhizophora Mucronata (rhizophoraceae) Lam. against Three Arthropods

The insecticidal and antifeedant activity of extracts derived from different parts of the mangrove tree Rhizophora mucronata (Rhizophoraceae) Lam. is reported. The 70% ethanol extracts of leaves, bark, stem wood and pith were tested for toxicity against adults of the desert locust Schistocerca gregaria (Forskal), the 2 instar larvae of Aedes aegypti (L.) and the 1 instar larvae of the brine shrimp Artemia salina (Leach). Antifeedant activity of the extracts was assessed through tests conducted on S. gregaria adults by the paper feeding protection bioassay. In tests carried out on A. aegypti mosquito larvae, bark and pith extracts showed high toxicity with 48 hour LC 50 ’s of 157.4 ppm and 168.3 ppm respectively. Stem wood extracts had low activity with an LC 50 of 1003.4 ppm while leaf extracts did not exhibit toxic effects at a concentration of 1000 ppm. A similar trend in activity was observed with antifeedant tests conducted on the desert locust S. gregaria and on toxicity tests carried out on A. salina larvae. The bulk of the active compounds are sequestered in the bark, pith and stem wood with the least being found in the leaves. The results indicate that R. mucronata is a potential source of botanical insecticides(s).