First report of powdery mildew caused by Erysiphe corylacearum on hazelnut in Bulgaria.

In June 2020, during an observation of fruit-bearing hazelnut trees (Corylus avelana L., cv. Tonda Gentile), grown in a small private home garden in the region of Kavarna (North-Eastern Black Sea coast of Bulgaria), symptoms of powdery mildew were observed on each of the 15 trees.