Chemical composition and antifungal activity of essential oils of Algerian Mentha species were studied. Chemical compositions of different Mentha species oils (Mentha rotundifolia, M. spicata, M. pulegium, and M. piperita) were investigated by capillary GC and GC/MS, and their antifungal activities were evaluated by means of paper disc diffusion method and minimum inhibitory concentration (MIC) assays. In total, 98 components from all Mentha species were identified. All oils were rich in monoterpene-oxygenated components. In addition, we reported fumigant antifungal activity of Algerian Mentha essential oils against four fungi: Botrytis cinerea, Penicillium expansum, Monilinia laxa, and M. fructigena. All oils demonstrated very good inhibition especially against B. cinerea, M. laxa, and M. fructigena. Both Monilinia fungi were extremely sensitive to all Algerian Mentha oils, which suggests that Mentha essential oils have the potential to be used as bio-pesticides to protect fruit trees, such as apple and pear trees, and provides an alternative to chemical pesticides.

Five plant extracts traditionally used in organic and biodynamic farming for pest control and antifungal (downy mildew) disease management were selected after a farmer survey and analyzed for their chemical composition in LC-PDA-MS-MS and using adapted analytical method from food chemistry for determination of class of component (e.g., protein, sugar, lipids…). Their antifungal activity against Penicillium expansum, Botrytis cinerea, Botrytis allii, brown rot causing agents (Monilinia laxa and Monilinia fructigena), and grape downy mildew (Plasmopara viticola) was examined in vitro. White willow (Salix alba) and absinthe (Artemisia absinthium) ethanolic extracts were found to be the most effective in particular against Plasmopara viticola, with a total inhibition of spores germination when applied at 1000 mg/L. These extracts also showed a relatively low toxicity during preliminary ecotoxicological assays on Daphnia pulex. Extract from the bark of white willow contained some flavonoids, especially flavanones (eriodyctiol and derivates) and flavanols (catechins and derivates), as major compounds, whereas absinthe extract was rich in O-methylated flavanols and hydroxycinnamic acids. Thujone content in this extract was also determined by external calibration in GC-MS analysis, and its value was 0.004% dry extract.