Silent killer..

The sight of Honey Fungus puts a chill into the heart of any gardener, as it's a silent killer of trees. This is one of several species of Honey Fungus, probably Armillaria gallica, which has a more bulbous stipe. It's a weaker pathogen than Armillaria mellea, which was abundant nearby, and is normally a secondary parasite. It was abundant over a dead stump at Old Sulehay Forest. 

In the woods Honey Fungus is a natural part of the ecosystem, and at Old Sulehay is particularly prolific in a stand of Sycamore, a tree which was introduced to the wood and has ousted the native Oak, Ash and Field Maple in a small area of the site. In this situation its deadly tendencies are to be welcomed, as it provides more dead trees, which themselves are homes to a myriad of invertebrates, not to mention hole-nesting birds such as Nuthatches. 

A clone of Armillaria gallica in Michigan was studied in the  in the early 1990s. Armillaria-infected oak trees had been harvested, and their stumps were left to rot in the field. Later, when red pines were planted in the same location, the seedlings were killed by the fungus. The DNA was analysed and the researchers determined that the underground mycelia of one individual fungal colony covered 15 ha (37 acres), weighing over 9,500 kilograms (21,000 lb), with an estimated age of 1,500 years. In their conclusion the authors noted: "This is the first report estimating the minimum size, mass, and age of an unambiguously defined fungal individual. Although the number of observations for plants and animals is much greater, members of the fungal kingdom should now be recognized as among the oldest and largest organisms on earth. After the paper was published, major media outlets from around the world visited the site where the specimens were found; as a result of this publicity, the individual acquired the epithet of the  "humongous fungus".