Potential of selected essential oils for the control of the european truffle beetle (Leiodes Cinnamomeus)

Abstract

The bioactivity of 14 essential oils extracted from semi- industrial pilot plant (table 1), were tested in vitro against one of the most important emergent pests of truffle plantations nowadays, the so-called European Black Truffle beetle Leiodes cinnamomeus in terms of repellent activity and contact toxicity. First, a preliminary screening was conducted using filter paper as carrier in both assays, in order to select the most promising plant species. For this purpose, 0.5% (v/v) and 400µg/insect were the initial doses. From this screening. Mentha rotundifolia, Satureja montana. Tanacetum vulgare and Origanum virens were the most effective in contact toxicity (100%); regarding repellent activity, this effect was observed, with a certain knock- down effect in most of the species chosen due to neurotoxicity of essential oils. In the light of these results, a follow-up toxicity dose-response experiment was undergone for filter paper formulation, in parallel with different formulations (alginate encapsulation and application on cellulose microfiber dishcloth) of the above mentioned 4 essential oils for the same doses. Activity assessed on cellulose microfiber dishcloths remained the highest after lowering doses to 100µg/insect. Also, another follow-up experiment was designed to better asses repellent activity. Dose was doubled in such oils where the knock-down was the lightest and halved in those where the knock-down was stronger. Nearly every oil saw its repellent activity enhanced following this strategy, thus dose-response experiments were undergone in those where the knock-down had been the greater. Again, the same 4 essential oils returned the best bioactivity and were diluted to 1/10 of the original dose. The same alternative formulations as for the toxicity assays were tested for such 4 essential oils, with remarkable differences in the bioactivity presented.