Accessions representing twenty eight landraces of maize were assessed for susceptibility to the maize weevil, Sitophilus zeamais in standardized resistance tests. Susceptibility parameters such as weight loss of grain, number of insect progeny produced, the Dobie index of susceptibility, and oviposition on grain were found to vary significantly by genotype, with exceptional resistance found in accessions representing the Naltel, Chapalote and Palomero landraces. As in improved genotypes, susceptibility was negatively correlated to phenolic and protein content of the variety tested but positively correlated to moisture content. A detailed analysis of the phenolics revealed the presence of diferulate which may contribute to mechanical resistance of the seed by cross-linking of cell wall hemicelluloses. A canonical discriminant analysis of the resistance data suggests that most of the five landrace groupings are significantly different. The ancient indigenous and prehistoric mestisos groupings are sources of resistant genotypes.

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Losses of stored seed to insects in the tropics have reached levels of major concern. Synthetic insecticides, while effective, are generally very expensive for small fanners. The efficacy of two plants, Hyptis spicigera and Cassia nigricans, used by farmers to control insect infestation in stored cowpeas was determined. The oviposition and hatching of bean weevils {Acanthoscelides obtectus), under controlled environmental conditions, were reduced following treatment with EtOH extracts (1 g plant material 1 ml EtOH) at low application rates with EC 50 between 0.3 and 14 n\ extract/g bean. Further field studies are proposed to determine if such natural products can be further exploited to reduce stored legume losses.Resume-Les pertes causees par les insectes aux graines entreposees ont atteint un niveau d'alerte. Les insectcides synthetiques bien qu'efflcaces sont generalement tres couteux pour les petits planteurs. On a determine l'efficacite de deux plantes Hyptis spicigera et Cassia nigricans utilisees par les planteurs pour lutter contre les infestations d'insectes attaquant les pois blancs. L'oviposition et l'eclosion des charancons (Acanthoscelides objectus) a des conditions d'elevage controlees a ete reduite suite a un traitement d'extraits alcooliques (un g/ml) a des doses faibles ayant une CE,,, de 0.3-14 ^1 d'extrait par gramme de pois. Nous proposons des evaluations sur le terrain pour determiner si Ton peut envisager l'utilisation de ce genre de produit naturel pour reduire les pertes en legumineuses emmagasinees.