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Apiosporina morbosa

[ Ascomycota > Venturiales > Venturiaceae > Apiosporina . . . ]

by Michael Kuo

Apiosporina morbosa doesn't cross most mushroom hunters' radar screens unless they are truly desperate to find and identify something fungal when mushrooms can't be found. However, the fungus is well known among those who keep orchards of cherry or plum trees; to these folks, it is a nasty little parasite known as "black knot." As a fungophile, I think Apiosporina morbosa is kind of cool, though I admit I own no cherry trees and the fungus is, um, not the most attractive woodland creature. In fact it looks a bit like dried cat poop on a stick. Outside of orchards and urban settings, Apiosporina morbosa is most often found on saplings of black cherry, throughout the range of the tree.

A related species, Apiosporina collinsii, produces a black leaf blight on serviceberry and Cotoneaster bushes.

Dibotryon morbosum is a synonym.


Ecology: Parasitic on the smaller branches of living cherry, plum, and date trees; in the woods usually found on saplings of black cherry; found year-round; originally described from North Carolina; widely distributed in North America but much more common east of the Rocky Mountains. The illustrated and described collections are from Michigan and Wisconsin.

Fruiting Body: 3–15 cm long; formed as an irregularly cylindric to spindle-shaped, knot-like growth surrounding small branches.

Outer Surface: Hard and crustlike; black; by maturity very finely pimply (use a lens) with perithecia; developing cracks with age.

Flesh: 2–5 mm thick; tough; white, becoming brown to black.

Odor: Not distinctive.

Microscopic Features: Spores 15–19 x 6–7.5 µm; clavate; smooth; septate with one septum near the narrow end; hyaline in KOH. Asci to 90 x 15 µm; cylindric to subclavate; 8-spored. Hyphae of the crustlike surface 2.5–7.5 µm wide; thick-walled; fragmenting easily; dark reddish brown in KOH.

REFERENCES: (L. D. von Schweinitz, 1822) J. A. von Arx, 1954. (Phillips, 1991/2005; McNeil, 2006; Zhang et al., 2011; Beug et al., 2014; Elliott & Stephenson, 2018; McKnight et al., 2021.) Herb. Kuo 09220408.

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Apiosporina morbosa

Apiosporina morbosa

Apiosporina morbosa

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Kuo, M. (2021, March). Apiosporina morbosa. Retrieved from the MushroomExpert.Com Web site: