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Significance of the disease

Armillaria root disease is often one of the most important diseases of trees in temperate regions of the world. The disease is important in native forests, planted forests, orchards, vineyards, and in amenity plantings in urban areas. The disease may also occur in nonwoody plants (Fig. 13). Substantial disease losses occur in temperate portions of North America, Europe, Asia, Japan, southern Africa, Australia, and New Zealand and certainly elsewhere. The disease also occurs in some tropical areas, including tropical portions of Africa, South America, and Sri Lanka, but in many cases it is less serious than in temperate areas, or occurs primarily at high elevations.

Fig. 13

Humongous fungus

Small fields like mycology and forest pathology can be turned upside down when something strikes the media's fancy on a slow news day. Such was the case in 1992 when a scientific article appeared highlighting the ability of Armillaria gallica to form very large clones, or genets. All it took was for the media to link that concept with the phrase, 'humongous fungus', and the hounds were released! A front-page headline article in The New York Times, a feature on ABC News with Peter Jennings, and David Letterman's Top Ten followed in quick succession (Fig. 14). Find more on this amusing story. Uhaul has a great web page on it, as it is one of the featured supergraphics on their rental vans. Even larger genets have been found. The largest to date is in eastern Oregon; it is about 900 hectares and estimated to be over 2,400 years old.

Fig. 14

Luminescence

Perhaps the most wonderful thing about Armillaria is that the mycelium, especially in actively decaying wood, is bioluminescent. Such glowing wood is known commonly as foxfire. There is a reference to it in the oldest surviving piece of English literature, Beowulf. Find more on this glow-in-the-dark fungus here.

You can easily see the luminescence by finding a stump or dead tree colonized by Armillaria. Look for bright whitish decay that is active and not invaded by other fungi. Chop out pieces and put them in a plastic bag. Collect a quantity, as the luminescence varies among pieces. Now find a place as dark as you can. To get you and your friends in the proper frame of mind, look at it in the forest on a cloudy (dark and stormy?) night. First let your eyes adjust to the darkness by telling a spooky story or two. Now unveil your collections, feast your eyes and amaze your friends!