Coral Spot

Description

Coral spot does not form typical mushrooms with a cap. On dead branches and twigs of broadleaved trees appear numerous small (a few millimetres), bright warts in orange or coral-pink, often clustered in large groups. With age they turn dark red to reddish brown and harden.

It is very common and can be found all year round on fallen branches and felled trunks, in forests, parks, orchards and gardens. It most often colonises dead or weakened wood, but it can also infect healthy trees through wounds, so in orchards and gardens it can be a nuisance.

It is usually told apart from similar Nectria species by the host and the colour of the cushions, but a reliable identification of some species requires a microscope. It is an inedible fungus, of no culinary importance.

Identification features

Cap

Absent; the species does not form a cap-bearing fruiting body. Small wart-like fruiting bodies (sporodochia) and perithecia develop on the bark.

Hymenophore (underside of the cap)

Absent (an ascomycete). The asexual stage forms sporodochia: bright orange, initially pinkish, wart-like pustules about 2–3 mm across (descriptions give 1–4 mm), which darken with age to reddish brown and harden. Beside them, and according to some descriptions within the sporodochia, carmine-red, hard perithecia 3.5–5 mm across develop, in which the ascospores are formed.

Stem

Absent.

Flesh

Not applicable; the fruiting bodies are small and hard, without typical flesh. Do not taste.

Spore print and spores

Conidia (asexual stage) single-celled, colourless, cylindrical-elliptical, 5–7 × 2–3 µm. Ascospores (sexual stage) 12–20 × 4.5–6.5 µm. Spore print colour: no data.

Habitat and distribution

Ecology. A saprotroph on dead wood and an occasional weak parasite of broadleaved trees and shrubs. It grows on branches and limbs that are drying out, weakened by frost, drought or a prior infection by other fungi; in warm, rainy weather it can also attack healthy trees and shrubs. It infects mainly through wounds (from pruning, storms, mechanical damage), less often through lenticels or roots in contact with infected wood. Hosts include beech, sycamore maple, horse chestnut and hornbeam; in orchard plants it causes shoot dieback, and the bark turns brown, sinks in and becomes covered with necrotic patches.

Distribution. Found on all continents except Antarctica, mainly in the cool temperate climate of the Northern Hemisphere. In Central Europe, including Poland, it is very common: in forests, thickets, parks and orchards. It is not legally protected in Poland.

Fruiting. All year round. Sporodochia (asexual stage) appear mainly in summer and autumn, perithecia usually from spring or early summer; sporodochia, mycelium and perithecia overwinter.

What can it be confused with?

• Nectria coryli (Polish: gruzełek leszczynowy) — Grows mainly on hazel, less often on poplars and willows; cushions dark red, later black.
• Nectria pinea (Polish: gruzełek sosnowy) — Occurs on conifers.
• Nectria sanguinea (Polish: gruzełek krwisty) — Grows most often on beech, less often on other broadleaved trees; cushions carmine-red or scarlet.

Never rely on a single feature. If you are not sure — do not pick it; show the mushroom to a qualified mushroom expert.

Interesting facts

• Described in 1791 by Heinrich Julius Tode as Sphaeria cinnabarina; its current genus name was given by Elias Fries in 1849.
• The English name “coral spot” refers to the coral, pinkish-orange warts on the bark.
• The same fungus occurs in two forms: asexual (orange sporodochia) and sexual (red perithecia), often side by side on the same branch.
• A 2011 study showed that the name N. cinnabarina covers a complex of at least four species.