Repellency and toxicity of essential oils from the leaves and bark of Laurelia sempervirens and Drimys winteri against Tribolium castaneum

We report here on the repellent activity, as well as contact and fumigant toxicity, of four essential oils extracted from the leaves and bark of Laurelia sempervirens and Drimys win ten against an important stored-product insect pest: the red flour beetle, Tribolium castaneum. The four oils tested had a very strong repellent activity towards T. castaneum when tested in a filter paper arena test. After 4 h exposure >90% repellency was achieved with L sempervirens oils at low concentrations of 0.032 mu l/cm(2), while for D. winteri oils concentrations of 3-10 times higher were needed to achieve this activity. Oils of both, L. sempervirens and D. winteri were found to be toxic towards T. castaneum when applied topically or by fumigation. LD50 values by topical application of L sempervirens oils were from 39 to 44 mu g/mg insect; for D. winteri oils these were from 75 to 85 mu g/mg insect. By fumigation, LC50 values fort. sempervirens oils were 1.6-1.7 mu l/l air, while these were 9.0-10.5 mu l/l air for D. winteri oils. In addition, with L sempervirens oils 50% of the tested beetles were killed at 100