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Toxicity ofChenopodium AmbrosioidesL. (Chenopodiaceae) Products From Nigeria Against Three Storage InsectsTests were carried out to study the toxicity, oviposition suppression, ovicidal and larvicidal effects ofChenopodium ambrosioidesL. as powder, extracts and essential oil againstCallosobruchus maculatusF. (Coleoptera: Bruchidae),Sitophilus zeamaisMotschulsky (Coleoptera: Curculionidae) andTribolium castaneumJacqueline du Val. (Coleoptera: Tenebrionidae). The powder formulation was more toxic toS. zeamaisthan eitherC. maculatusorT. castaneumwith 48 h LC50values of 0.46 g/kg, 1.60 g/kg and 2.14 g/kg, respectively. Ethanol extract was more toxic toC. maculatuswith a 48 h LC50value of 0.023 g/l, than other test insect species. The essential oil treatment demonstrated higher fumigant toxicity againstC. maculatusthanS. zeamaiswith 24 h LC50values of 1.33 μl/l and 1.90 μl/l respectively. The oil vapour showed activity againstC. maculatusegg, but had no appreciable larval mortality. The weight loss of grains admixed withC. ambrosioidespowder was lower than the controls after 150 days of field storage.

Studies on the morphology and distribution, and the role of trichomes in damage to cowpea (Vigna unguiculata) by the legume pod borer Maruca testulalis (Geyer) showed that trichome cover on individual cultivars varied in trichome length and density, but not in trichome type from different plant parts. Trichome density on different parts decreased with increasing plant age. Significant (P <0.05) negative correlations were obtained between total trichome density on pods, pod infestation and damage severity. In contrast, correlations between length of non-glandular trichomes on pods, pod infestation and damage severity were not significant. Results suggest that trichome length may be less important than density in reducing pod damage by M. testulalis in cultivated cowpeas. It is, therefore, concluded that breeding for a higher level of trichomes in high yielding and agronomically desirable cowpea cultivars, will serve as an important component in the integrated management of M. testulalis.

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