Essential oils used against zucchini powdery mildew: evaluation of variability in chemical composition and bioactivity

Trend in the reduction on use of synthetic pesticides is continuously growing. Their substitution with natural substances is well studied because of the environmental vantages. Consumers require safe foods. Their risk perception concerns the presence of synthetic pesticides and marketing is oriented toward food with lower and lower residue levels. Essential oils (EOs) could be a reliable alternative. Their components are in a variable range of concentrations determining, in some cases, for the chemotypes. Lots of rosemary, oregano, and clove oil were purchased on the market and their main components were analyzed. Four EOs formulations were prepared to test their effectiveness against zucchini powdery mildew. Moreover, rosemary leaves were collected from the CREA-DC garden (Rome) and rosemary essential oil, distilled in-house, in combination with oregano essential oil were also tested. Metrafenone and penconazole were synthetic fungicides used for reference treatments. Two trials were carried out in a greenhouse.