Four different concentrations of extracts, obtained from the two lichen species (Cladonia foliacea (Huds.) Willd. and Flavoparmelia caperata (L.) Hale), were tested against the grain weevil, Sitophilus granaries (L.) under laboratory conditions. Mortality rate of adults was determined at 24, 48, and 96 h. Obtained results showed that the extracts of C. foliacea and F. caperata had insecticidal effects on the adults of S. granarius in comparison with control. The insecticidal effect was influenced by the concentration of the extract and the exposure time. Higher concentrations and longer exposure time resulted to highest toxicity levels on S. granarius. Mortality rates after 96 h of treatment with highest concentration (20 mg.ml(-1)) of the extracts of F. caperata and C. foliacea were determined as 91 and 83%, respectively. Bioassay revealed that 96 h LC50 values were 0.107 and 0.354 mg.ml(-1), respectively. The results suggest that lichen compounds could be useful as alternatives of pesticides.