Monilinia johnsonii (Ellis & Everh.) Honey    

Kingdom: Fungi
Phylum: Ascomycota
Subphylum: Pezizomycotina
Class: Leotiomycetes
Order: Helotiales

British distribution: Widespread, undoubtedly under-recorded.
World distribution: Europe, North America, no doubt elsewhere.

A fungal pathogen of hawthorns (Crataegus, in Britain on C. monogyna and C. laevigata).

Monilinia johnsonii:  apothecia on old Crataegus monogyne fruits
Monilinia johnsonii: apothecia on old, "mummified" fruits of Hawthorn (Crataegus monogyna), Blantyre, Lanarkshire, 1985.

The sexual fruit-bodies (apothecia with inoperculate asci) occur on old berries (haws) of hawthorn, in the litter in Spring, but it is usually necessary to crawl in under the trees to find them. The apothecia are stalked, presumably to enable the cups to push up to the litter surface from mummified berries that are well buried.

The anamorphic (asexual) stage is assigned to the form-genus Monilia. Effuse, sweet-smelling, grey to buff patches form on the living leaves, producing globose conidia in chains, and causing large, brown to black, necrotised areas in the leaf.

Useful descriptions of the sexual and asexual stages are provided in Seaver (1951) and Dennis (1981). Related species occur on fruit trees of the rose family (Prunus, Malus, Mespilus, etc., Rosaceae) and on species of bilberry (Vaccinium) in the Ericaceae.

•   Dennis, R.W.G., (1937). British ascomycetes, ed. 2, 2nd impression (updated), J. Cramer, Vaduz.
•   Seaver, F.J., (1937). The North-American cup-fungi (Inoperculates), privately published, New York.

© A.J. Silverside
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