mulberry leaf spot (popcorn disease)

Symptoms

Pale brown angular spots between leaf veins, spots darken and develop pale centers, premature leaf yellowing and drop in late summer, slight yield loss.

Easily confused with

• mulberry bacterial blight

  How to tell them apart: Mycosphaerella mori (fungal mulberry leaf spot / 'popcorn' false mildew) and Pseudomonas mori (bacterial blight of mulberry) both start as small dark spots on mulberry leaves. Mycosphaerella mori spots are roundish, brown to grey-brown with a darker margin and stay scattered across the blade; in humid weather tiny black pinhead fruiting bodies (pycnidia/perithecia) and a whitish-grey felty bloom appear on the spot surface, and the lesion edge is diffuse rather than vein-bound. Pseudomonas mori spots are instead angular and water-soaked, sharply confined by the leaf veins, often with a translucent yellow (chlorotic) halo; in wet conditions they exude sticky bacterial ooze, turn the leaf greasy/blackish and run along petioles and young shoots as dark sunken streaks, with no powdery growth or visible fungal bodies.