Willow Tarspot - Rhytisma salicinum

Description

This fungus causes a raised shiny black spot to appear on the leaves of certain willows. Initially seen is usually the stroma, a thickened, blackened region of the leaf tissue, though this is preceded by smaller black spots about 1mm in diameter, the anamorphic (asexual) stage.

Identification difficulty
Habitat

Where the host trees (mainly Goat Willow, Grey Willow, Eared Willow and hybrids) occur. It seems to occur mainly in rural areas, the fungus seemingly being less tolerant of atmospheric pollution than its well-known relative Sycamore Tarspot.

When to see it

When the host trees are in leaf.

Life History

After leaf-fall, the stromatic area survives over winter and apothecia develop in spring, several per stroma, pushing through splits in the original leaf epidermal tissue to release spores in time to infect the new young leaves of the host.

UK Status

Widespread in Britain though less frequent than its relative Sycamore Tarspot.

VC55 Status

Status in Leicestershire and Rutland not known.

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Leicestershire & Rutland Map

MAP KEY:

Yellow squares = NBN records (all known data)
Coloured circles = NatureSpot records: 2020+ | 2015-2019 | pre-2015

UK Map