Studies on the efficacy of electrolysed oxidising water to control Aspergillus carbonarius and ochratoxin A contamination on grape

Abstract

Ochratoxin A (OTA) occurrence in grapes is caused by black Aspergilli (Aspergillus carbonarius followed by A. niger) vineyards contamination. It depends on climatic conditions, geographical regions, damage by insects, and grape varieties. Good agricultural practices, pesticides, and fungicides seem adequate to manage the problem during low OTA risk vintages, but the development of new strategies is always encouraged, especially when an extremely favourable condition occurs in the vineyard. Electrolysed oxidising water (EOW) has become an interesting alternative to chemicals in agriculture, mainly during the post-harvest phase. This study tested the fungicidal efficacy of EOW generated by potassium chloride, in vitro, on black Aspergilli conidia, and detached grape berries infected by A. carbonarius. Then, during field trials on Primitivo cv vineyard treated with EOW, A. carbonarius contamination, and OTA levels were compared with Switch® fungicide treatment (0.8 g/l). Black Aspergilli conidia were killed on plate assay after 2 min of treatment by EOW containing >0.4 g/l of active chlorine. EOW (0.6 g/l active chlorine) treatment reduced the rate of A. carbonarius infections in vitro of about 87-92% on detached berries and, more than half in the field trials, although Switch® showed better performance. A significant reduction in the OTA concentration was observed for the EOW and Switch® treatments in vitro (92% and 96%, respectively), while in the field trials, although the average decrease in OTA was recorded in the treated grapes, it was not statistically significant. These results highlighted that EOW could be considered effective, as a substitute for fungicides, to reduce the contamination of A. carbonarius and OTA on grapes.

Keywords: Aspergillus carbonarius; Black Aspergilli control; Electrolysed water; Grape berries; OTA contamination; Vineyard treatment.