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 Printable version |
Bioefficacy of powders and essential oils from leaves of
Chenopodium ambrosioides and
Eucalyptus saligna to the cowpea bruchid,
Callosobruchus maculatus Fab. (Coleoptera, Bruchidae) |
Cahiers Agricultures. Volume 12, Number 6, 401-7, Novembre-Décembre 2003, Étude originale
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 Résumé
Article gratuit
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Author(s) : Leon Azefack Tapondjou, Cornel Adler, Hamilton Bouda, Dominic Ajong Fontem |
Summary : Cowpea seeds
(Vigna unguiculata) protection in the tropics is usually handicapped by storage losses caused by insect infestation. Small‐scale farmers commonly use local plant materials to protect their stored grain from insect damage in sub‐tropical african countries. The leaves of
Eucalyptus saligna and
Chenopodium ambrosioides mainly used as cowpea grain protectants by communities of the Western highlands of Cameroon are a powerful source of essential oils. The volatile oils extracted by steam distillation from the leaves of both plants were analysed by GC‐MS and evaluated along with their leaf powders for their insecticidal activities against the cowpea bruchid,
Callosobruchus maculatus Fab. Tests of contact toxicity of the powders and essential oils in treated grains, tests of contact toxicity and repellency of essential oils on filter paper were carried out in a controlled temperature and humidity chamber (25 to 27°C, 70 to 75% RH). The powders and essential oils from both plants had insecticidal and repellent properties against
C. maculatus. Those derived from the leaves of
C. ambrosioides were more toxic (DL
50 ∓ 2.8 g\\kg for powder and 0.17 µL\\g grains for essential oil) than those of
E. saligna (DL
50 ∓ 322 g\\kg for powder and 0,19 µL\\g grains for essential oil) in treated grains. The chemical analysis of the oil revealed that they are mainly constituted of compounds such as ascaridole whose insecticidal activities have previously been demonstrated, thus indicating a possible scientific rationale for the empirical use of these plants as grain protectants by small‐scale farmers in the Western highlands of Cameroon. |
Keywords : Phytosanitary protection. |
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