Essential oils contacttoxicity towards O. surinamensis and T. castaneum
adults was measured according to Liu and Ho (1999). A
serial dilution of the essential oil was prepared in acetone (0.1 ml).
1 l of aliquots dilutions were deposited topically to dorsal thorax
of beetles. Acetone was used as a check trial. After that, treated and
control insects with culture media (2 g) were placed into Plexiglass
bottles (10 beetles/bottle). Each concentration was repeated four
times. Mortality was observed each hour til end-point. The LD50
values were estimated using probit analysis