In this study, the antifeedant, growth and toxicity effects of some plant extracts derived from Liguidamber orientalis Mill. (Hamamelidaceae), Ocimum basilicum L. (Lamiaceae), Hypericum perforatum L. (Hypericaceae), Tanacetum vulgare L. (Asteraceae), Origanum vulgare L. (Lamiaceae), Sambucus nigra L. (Caprifoliaceae), Alnus glutinosa L. (Betulaceae), Arum italicum Mill. (Araceae), Artemisia absinthium L. (Asteraceae), Achillea coarctata L. (Asteraceae), Erica arborea L. (Ericaceae), Rhus coriaria L. (Anacardiaceae), Buxus sempervirens L. (Buxaceae), Colitea aborescens Strauch. (Fabaceae) and Aesculus hippocastanum L. (Hippocastanaceae) are reported. In the tests, carried out with the larvae (1.-4. instar) and adults of Leptinotarsa decemlineata, extracts from A. hippocastanum, T. vulgare and A. absinthium showed a high toxicity rate in 48 hours, and LC50's of 33.3, 33.3 and 26.6%, respectively. No mortality was determined in control groups. Alcohol extracts from B. sempervirens and A. absinthium showed a high antifeedant activity rate (92.77 and 88.23%) on the larvae (instar 1) of L. decemlineata, whereas that of R. coriaria showed high antifeedant activity /77.77%) on the larvae (instar 4) of L. decemlineata. L. orientalis and B. sempervirens showed 77.77 and 60%, respectively, on the adults of L decemlineata. B. sempervirens, L orientalis, A. absinthium and R. coriaria extracts caused body weight decreases per mg of larvae's food consumption (instar 1), and the highest values were -12.9, -12, -11.7 and -9.4 mg, respectively. The same effects had C. aborescens and B. sempervirens extracts causing upto -21.3 and -17.5 mg decreases per mg of larvae's food consumption (instar 4), whereas alcohol extracts from O. basillicum caused. 12.30 mg body weight increase per mg of larvae's (instar 4) food consumption.