entomosporium leaf spot

Symptoms

Small purple-red spots with grey centers on young leaves, spots merge into larger lesions, defoliation in severe years, fruit blemishes on loquat.

Easily confused with

• pear brown spot
• fire blight

  How to tell them apart: Diplocarpon mespili (Entomosporium leaf spot) shows many small, discrete circular-to-angular spots scattered over the leaf blade, each reddish-purple to brown with a darker margin; as spots mature you can see tiny black pinhead fruiting bodies (acervuli) in the centre, and heavy infection turns leaves reddish and causes early leaf drop, but twigs and shoots stay alive. Erwinia amylovora (fire blight) does NOT make scattered round spots — instead whole shoot tips, flowers and leaves brown or blacken and die together from the tip downward, the leaves stay attached and hang as if scorched by fire, young shoots bend over into a characteristic 'shepherd's crook', and in warm humid weather milky-amber bacterial ooze droplets appear on infected stems and fruitlets. Key tell: many separate spots with black dots = leaf spot fungus; a continuous brown/black dieback running down the shoot with a hooked tip and sticky ooze = fire blight. Fire blight is an EU-regulated quarantine bacterium and must be reported.

• bacterial blight / canker (multi-host)

  How to tell them apart: On Photinia × fraseri, Diplocarpon mespili (Entomosporium leaf spot) starts as tiny round bright-red to maroon spots scattered on both old and new leaves; as they age the centres turn grey-brown and develop a minute glossy black pinhead-sized fruiting body (acervulus) in the middle — use a hand lens to find this raised black dot, which is diagnostic and absent in bacterial disease. Pseudomonas syringae pv. syringae instead makes darker brown-to-black angular spots that are limited by the leaf veins, often water-soaked and translucent at the margin when held to the light, sometimes with a thin yellow halo, and appears mainly in cool wet spring weather on young shoots and leaf edges, frequently with twig dieback and no black fruiting dot. In short: look for the central glossy black speck and round red spots for Entomosporium, versus angular vein-limited water-soaked spots with shoot dieback for Pseudomonas.

• cherry powdery mildew

  How to tell them apart: Both attack hawthorn leaves but look different. Podosphaera clandestina (hawthorn powdery mildew) is a superficial white-to-grey powdery felt that sits ON TOP of the leaf, rubs off with a finger, and distorts young shoot tips. Diplocarpon mespili (entomosporium leaf spot) makes discrete purple-red to brown spots with paler grey centres embedded IN the leaf tissue — they do not wipe off, often carry a tiny dark pimple (acervulus) in the centre, merge into blotches and cause heavy leaf drop rather than distorted shoots.