Effect of mite biological control on the physicochemical properties and bioactive compounds profile in grapes of Merlot variety

Vineyards are a favorable culture for the habitat of phytophagous mites. These pests feed on the cellular sap of vegetables, causing damage to plants. The aim of this study was to comparatively evaluate the effects of applied biological control of Panonychus ulmi (Koch) (Tetranychidae) using Neoseiulus californicus (McGregor) (Phytoseiidae) on the physicochemical properties and bioactive compounds profile in grapes of Merlot variety, in one single property in the municipality of Bento Gonçalves, Rio Grande do Sul, Brazil. Treatments were conducted in three different areas of the vineyard: area attacked by P. ulmi (AP), area with P. ulmi controlled by N. californicus (APN), and a third area without the presence of mites (AWM). Berries in the AP treatment had lower hardness, with both test probes used (cutting line type and cylinder type). Grapes of AWM treatment had higher red coloration in parameter ‘a*’, both in the skin and in the pulp. Sugar content did not significantly differ between fruits from grapevines with presence of mites. In grape skins of AP treatment, total phenol, flavonoid, and anthocyanin contents were significantly higher, whereas resveratrol content was lower. Compared to fruits of grapevines without mites (AWM treatment), grapes with biological treatment (APN) had significantly higher contents of sugar, total phenols (pulp and skin), flavonoids (skin), anthocyanins (skin), and antioxidants (skin and pulp). Results suggest that biological control applied using predatory mites increases the concentration of phenolic compounds in fruits, improving the nutritional quality of the grapes.