Downy mildew | A fungal disease of vine fruit & foliage caused by biotic factors. In Europe it is more often referred to as peronospera (or ‘pero’ for short). Downy mildew affects the leaves, fruit, and shoots of grapevines, causing decreased berry production and production of poor quality wine (Ian D’Agata, 2014).
Dr Ian D’Agata, Native Wine Grapes of Italy (University of California Press, 2014), p569.
The Oxford Companion to Wine 4th edition ed. Jancis Robinson MW and Julia Harding MW (Oxford University Press, 2015), p543.