Effects of Extracts and Hydrodistillates of Clausena anisata (Wild.) ex. Benth. and Hyptis spicigera Lam. on Musca domestica L. and Periplaneta americana (L.)

Abstract

Extracts of two indigenous Ghanaian medicinal plants Clausena anisata and Hyptis spicigera were bioassayed against housefly (Musca domestica L.) and cockroach (Periplaneta americana (L)) for various insect control activity. The extractives bioassayed were the petroleum ether and methanol extracts and essential oil of the plants. The lethal toxicity of the plant extractives were bioassayed using topical application and petri dish residual method against adult flies and cockroach nymphs respectively. The essential oils exhibited knockdown effect when they were bioassayed against housefly by topical application. A treated filter paper method was used to evaluate the repellency of the extractives against housefly. The crude extracts were also bioassayed for growth regulatory effect against the second larval instar of housefly using a treated larval breeding medium. A treated rearing medium method was also used to test the antifeedant effect of the crude extracts against cockroaches. Per cent mortality, knockdown and index of repellency induced by the extractives against the insects were generally dose-dependent. The essential oil of the two plants were however more effective as toxicants and repellents than the crude extracts. The LD50 of the essential oil of C. anisata and spicigera were 2.2101 and 0.8580 μg respectively, against flies and 0.0096 and 0.0310 /μg cm-2 respectively against cockroach nymphs. The LD50 of the solvent extractives ranged between 0.4143 and 1746.2 mg for housefly and 0.6869 to 2.600 mg cm-2 for cockroach The knockdown potency of essential oils from H. spicigera (KD50= 0.2631) was better than for C. anisata (KD50 — 0.7445). The RD50 of C. anisata and H. spicigera in 30 min were 0.0400 and 0.0509 μg cm-2 against housefly. The RD50 of the crude extracts ranged from 0.1288 to 1.3768 mg cm-2 against housefly. The crude extracts however demonstrated poor growth regulatory and antifeedant effects.