As part of on-going efforts to use eco-friendly alternatives to chemical pesticides, ethanolic extract of dried leaves of Dracaena arborea (Willd.) Link (Dragon tree; Dracaenaceae) dissolved in distilled water and partitioned between equal volumes of n-hexane, chloroform, ethyl acetate and butanol was assessed in the laboratory against infestation by Sitophillus zeamais Motsch. and Callosobruchus maculatus Walp. in stored maize and cowpea, respectively. One hundred grams each of maize grains and cowpea seeds were treated with 400 mg kg(-1) of each extract fraction to evaluate contact toxicity, damage assessment, effect on eggs and immature stages and progeny production in both insect species. Contact toxicity by topical application, toxicity upon filter paper application and repellency using area preference method were carried out on the two insect species. Results showed that the extract fraction caused significant (p < or = 0.05) mortality of both insect pests with a high residual contact activity against S. zeamais. Grain damage was significantly (p < or = 0.01) reduced, while progeny production and development of eggs within grains were inhibited. The extract fractions evoked a strong repellent action against S. zeamais but moderate action against C. maculatus. The full potentials of using extract fractions of D. arborea as grain protectant against infestation by insect pests is discussed.

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Studies were carried out in the laboratory to determine the efficacy of powders from plant parts of Ricinodendron heudelotii against the storage pests Sitophilus zeamais and Callosobruchus maculatus on stored maize and cowpea, respectively. Leaf, bark and root powders were added as admixtures to 100 g of grains to assess contact toxicity, damage assessment, progeny production and grain germination. Results indicated that the plant materials were toxic to the two insect species with over 30% and 75% mortality for S. zeamais and C. maculatus, respectively. Observable damage level was significantly (p ≤ 0.05) lower in treated grains while progeny production by both insect species was significantly (p ≤ 0.05) reduced. Grain germination of both crops was not affected by the powders. The potential use of P. heudelotii in storage pest management is discussed.