The control of isariopsis leaf spot and downy mildew in grapevine cv. Isabel with the essential oil of lemon grass and the activity of defensive enzymes in response to the essential oil

• The research describes the potential of essential oil for alternative control of diseases of grapevine.
• The essential oil of lemon grass reduced the severity of isariopsis leaf spot and downy mildew in grapevine cv. Isabel.
• The increased activity of enzymes, chitinase and catalase indicates the elicitor action of essential oil in grapevine.

The aim of this study was to evaluate the potential of the essential oil of lemon grass (Cymbopogon citratus) for the control of isariopsis leaf spot (Pseudocercospora vitis) and downy mildew (Plasmopara viticola) in grapevine cv. Isabel, the effect of the essential oil on the productivity of the grapevines and the effect of the essential oil on the activity of the enzymes chitinase and catalase. The experiment was conducted in a commercial vineyard over two consecutive crop cycles. Each plant in the experiment was subjected to one of the following nine treatments: 0, 0.5, 1.0, 2.0 or 4.0 mL L−1 essential oil, Tween® 80%, Bordeaux mixture, Acibenzolar-S-methyl and mancozeb. An analysis of the area under the disease progress curve showed a quadratic response by both diseases to the doses of essential oil during the first and second crop cycles. The essential oil treatments also increased the number and mass of the clusters of fruit as well as the productivity and desirable chemical characteristics of the grape. The activity of chitinase increased as a result of the essential oil treatments, whereas the activity of catalase decreased. The essential oil at doses of 1.0 and 2.0 mL L−1 can serve as an alternative means of controlling isariopsis leaf spot and downy mildew and can also serve to improve the fruit quality of grapes cv. Isabel in tropical regions.