THE EFFECT OF WATER EXTRACT FROM WILD THYME ON COLORADO POTATO BEETLE FEEDING

The aim of this study was to determine the effect of water extracts prepared from fresh and dry matter of wild thyme (Thymus serpyllum L.) on feeding adults and larvae of Colorado potato beetle (Leptinotarsa decemlineata Say.). The experiment was conducted in the laboratory, in six replicates. Dry extracts were prepared at concentration of 2%, 5% and 10%, while the fresh plant at concentration of 10%, 20% and 30%. Feeding intensity assessment was conducted by dipping leaves of potato in respective solutions of the extracts and determining the mass of food consumed by adults and larvae, and changes of larvae body weight once daily. In addition, absolute deterrence index and palatability index were calculated. The results of the experiment showed that for an efficient limitation of the feeding adult Colorado potato beetles, an extract from dry matter of wild thyme with a concentration of at least 10% should be used. L4 larvae appear to be considerably more susceptible to the effect of T. serpyllum extract. In their case, an efficient limitation of the feeding, as well as body weight gain can be obtained using extracts from both dry and fresh matter, at concentrations of over 5% for dry matter and over 20% for fresh matter. With the increase of extract concentration, the value of the calculated palatability index decreases, and the deterrence index value increases.