Lower dose of plant substance more effective in repelling Rhyzopertha dominica F . (Coleoptera, Bostrichidae) and Sitophilus granarius L. (Coleoptera, Dryophthoridae).

Abstract

The study compares the effect of two concentrations (0.1% and 1%) of plant material on repelling two dangerous stored pests - Rhyzopertha dominica F. and Sitophilus granarius L. Both species were treated with the essential oils of Foeniculum vulgare Mill., Carum carvi L., Mentha pulegium L., and Cananga odorata (Lam.) Hook.f. & Thomson, as well as the chemicals contained in these oils: anethole, L-carvone, pulegone and thymoquinone. Laboratory tests were carried out at 29±1 °C with 60±5% relative humidity (RH). Repellence of insects were noted after 1, 2, 3, 4, 5, 24 and 48 h. A lower dose of essential oils and some of the tested compounds caused a stronger repellence in the specified species of beetles. In the case of R. dominica, the concentration of 0.1% pulegone and L-carvone had the greatest repellent effect. Differences in the repellence of R. dominica were found between the concentrations of 0.1%-1% among all the tested substances in each time interval. This difference ranged from 5.0%-52.92%. All substances used in the tests had a strong repellent effect on S. granarius (30%-100%). There were differences in the repellency of S. granarius between 0.1%-1% concentration in most of the tested substances in each time interval, but they were not as large as for R. dominica.. The most interesting results were obtained concerning the relationship: the lower tested substance concentration caused a much stronger repellent effect of R. dominica and S. granarius..