The antifeedant activity of lactones with di- and trimethylcyclohexane system was assessed in choice and no-choice bioassays against Leptinotarsa decemlineata and Alphitobius diaperinus larvae and beetles. The results showed that feeding deterrent activity depends on the structure of the tested compounds. Additional methyl group in the molecule of some compounds influences their activity increase or changes their properties from attractant to deterrent ones. The present results also demonstrate the species and developmental stage dependence of antifeedant activity.

The effect of some terpenoid lactones (monocyclic ó-hydroxy-v-lactone: bicyclic &-hydroxy-y-spirolactone and bicyclic &-hydroxy-y-lactone) and azadirachtin on feeding and growth of Leptinotarsa decemlineata Say larvae was studied. Among lactones bicyclic 6-hydroxy-y-spirolactone showed a strong feeding deterrency. Larvae treated with this compound consumed O.I63 cm2 (per larva) of potato leaves during 6 days, whereas control larvae ate 0.892 cm2• When lactones were used, a slight increase in body weight was observed. Azadirachtin, in comparison with lactones, much stronger reduced food consumption and growth rate of insects.