Potency to Cowpea Seed Bruchid, Callosobruchus maculatus (Fabricius) [Coleoptera: Bruchidae], of African Nutmeg Seed [Monodora myristica (Gaertn.) Dunal] Extracted with Different Solvents.

Abstract

African nutmeg, Monodora myristica (Gaertn.) Dunal, seed was extracted using: methanol, ethanol, acetone. petroleum-ether. n-hexane or water. The extracts were tested for insecticidal activity against cowpea seed bruchid, Callosobruchus maculatus (Fab.), at ambient tropical conditions of temperature and relative humidity. Results showed that steam distillate caused the highest percentage mortality (92.5 ± 0.80) at 4 days post-treatment compared to 40.0 ± 0.8 – 68.8 ± 1.0 for other solvents. However, only acetone caused significantly (P<0.05) lower mortality. When the bruchids had choice of oviposition substrate, they laid significantly fewer eggs (18.8 ± 0.8) on cowpea seeds treated with steam distillate compared to 2: 32.8 ± 1.8 eggs laid on cowpea seeds treated with other solvent extracts. Significantly lower number of adults emerged from seeds treated with extracts than from untreated seeds. There was no adult emergence in seeds treated with steam distillate, therefore suggesting that steam distillate was the most potent of all biopesticide tested for insecticidal activity on C. maculatus.