Effects of material and extracts of Trigonella foenum-graecum L. against the stored product pests Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and Acanthoscelides obtectus (say) (Coleoptera: Bruchidae)
Résumé
Insecticidal activity of plant material (seeds and leaves) and extracts of Trigonella foenum-graecum from two sources against the stored product pests Tribolium castaneum and Acanthoscelides obtectus was investigated. Topical applications of extracts produced a high degree of mortality in both insects (at 6 and 30 μg/insect). Powdered fenugreek seeds or extracts applied to Phaseolus vulgaris beans produced mortality and inhibited oviposition and larval penetration by A. obtectus. The presence of the plant material decreased A. obtectus fecundity and reduced its longevity. Fenugreek seed appeared moderately toxic to young larvae of T. castaneum (LD25 = 18% in diet), and surviving adults showed progressively decreased fecundity as the dose of seeds, especially ripe seed, was increased. Significant effects of dose, seed ripeness and their interaction were produced. The seed affected the fertility of both sexes. Some fertility was recovered on reversion to the standard diet. Possible active compounds and the implications of the results for pest control are discussed.