The Carlisle Mosquito Online

Friday, February 12, 2010


Coral Spot

Name: The Coral Spot fungus is something any of us might find in our back yards and is something any of us might have named. If you come upon a hardwood stick harboring this

Coral Spot fungus (Photo by Kay Fairweather)

fungus, you would probably describe the stick as covered with little coral-colored spots. In the binomial system of naming, things get a bit complicated. For most organisms, the binomial name is unique to the species. However, there are about 5000 fungal species (so far) which have two binomials. The Coral Spot is one of them.

When and where found: Last week, my neighbor on School Street, Jon Golden, found in his yard some dead maple sticks covered with the Coral Spot fungus. It is probable that the fungus did not kill the maple. Coral Spot is a weak parasite of living trees. It grows more vigorously on wood that is already dead and so this is where you are most likely to notice it. It can appear on a variety of different hardwood species with maple being a frequent host. It is quite common and can be found all year round.

Distinguishing characteristics: The individual coral spots tend to be about a quarter of an inch across. They are raised above the surface and sit there like little cushions. The color varies from pinkish-coral to orange and can be quite vivid. In winter time, if you look more closely, you will likely see smaller dark red globules either singly or in dense clusters growing in, on, or near the coral spots. The red globules are spore-producing structures. As they mature, they become a dull reddish-brown and develop a nipple on the top which opens to release the spores. Jon Golden’s maple stick had both the larger coral cushions and the little red globes.

Reproduction: Fungi reproduce by creating spores. The Coral Spot is in the group called Ascomycetes where the spores are created in sacs called ‘asci’. But many Ascomycetes also have an asexual phase in which they produce different spores called conidia. The curious thing is that the sexual phase (called the teleomorph) and the asexual phase (called the anamorph) can develop on different substrates and at different times. This means that samples of these fungi have been collected, described and named in complete ignorance of the existence of the other form. In the case of Coral Spot, the anamorph, which is the more readily visible coral cushion, is named Tubercularia vulgaris and the teleomorph, which is the red globular form is named Nectria cinnibarina. When both forms appear together, the name defaults to that of the teleomorph. The Coral Spot anamorph is the typical summer state of the fungus and is a prolific producer of conidia. The Coral Spot teleomorph is the form capable of producing winter-hardy spores. Many thousands of species of anamorphic fungi have not yet been connected with any teleomorph. They seem to have developed a completely asexual lifestyle reproducing only via conidia but they have retained a few tricks that allow for genetic flexibility.

Why care about conidial fungi? These fungi can grow on you – literally. The most common fungal diseases of humans are caused by conidial fungi. Also the troublesome black mold called Stachybotrys chartarum is another member of the clan, along with Aspergillus flavus which produces the most potent known carcinogen and Fusarium which causes wilt disease in plants. But it’s not all bad. Penicillin, cyclosporine, and their derivatives which are hugely beneficial to mankind also came from conidial fungi.

References: Mushrooms of Northeast North America – Midwest to New England, George Barron; Mushrooms of Northeastern North America, Bessette, Bessette & Fischer; Fungi, the Fifth Kingdom, Bryce Kendrick. ∆

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