Essential oils: an alternative approach to management of powdery mildew diseases.

In recent years there has been growing interest in the application of plant-derived substances in agriculture as alternatives to the use of pesticides, in order to obtain healthy crops and more environmentally sustainable crop production systems. The properties of some essential oils as natural fungicides were evaluated, to promote their use in alternative agriculture. Potentially detrimental effects caused by essential oil residues in soil were also assessed by mutagenicity assays to avoid possible adverse effects related to the use of these materials. Trials in a controlled environment were set up, using ‘Romanesco’ zucchini treated with essential oils, either exclusively or alternated with a synthetic fungicide. The treatments were applied when natural infection by Podosphaera xanthii appeared on test plants, and powdery mildew incidence and severity were assessed after six weeks. Preliminary results indicated that the alternation of natural materials with effective synthetic fungicide maintained effective disease control, and may also assist with management of pesticide resistance in P. xanthii . No relevant mutagenic effects of essential oil residues in soil were revealed, although an appropriate formulation useful under field conditions is required for effective application.