Repellent activity of some essential oils against two stored product beetles Callosobruchus chinensis L. and C. maculatus F. (Coleoptera: Bruchidae) with reference to Chenopodium ambrosioides L. oil for the safety of pigeon pea seeds

Essential oils from 35 aromatic and medicinal plant species of Gorakhpur Division (U. P., India) were evaluated for their repellent activity against pulse bruchids Callosobruchus chinensis L. and C. maculatus F. of stored pigeon pea seeds. The oil concentration was at 0.36 μl/ml. Out of 35 essential oils, Adhatoda vasica Ness and Chenopodium ambrosioides L. oils showed absolute (100 %) insect repellency. Chenopodium oil exhibited 100 % mortality for both the test insects at 10 μl concentration (LD50 = 2.8 μl for C. chinensis & 2.5 μl for C. maculatus) and more toxic than Adhatoda oil (LD50 = 6.8 μl for C. chinensis & 8.4 μl for C. maculatus). During in vivo evaluation, 0.29 and 0.58 μl/ml of Chenopodium oil significantly enhanced feeding deterrence in insects and reduced the seed damage as well as weight loss of fumigated pigeon pea seeds up to 6 months of storage as compared to control set. Thus, Chenopodium oil can be used as an effective option of commercial fumigants for the storage of pigeon pea seeds against pulse bruchids.