base of the trunk or from the soil over decaying roots. They are produced from July to January, are not perennial and become black and slimy when exposed to frost.
Chicken-of-the-woods or Sulphur Polypore (Laetiporus sulphureus)
Commonly found on oak and yew. Often found causing a top rot, but can also affect the lower trunk and roots. Causes a brown rot of the heartwood, but this progresses quite slowly and it may be several years before parts of the tree become unsafe. The fruiting bodies are very characteristic brackets or fronds with wavy edges, often found in groups. They are bright yellow when first produced, eventually fading to a creamy-white. They are produced annually from May to November.
Ganoderma species
One of the most common groups of decay fungi. There are a number of species of Ganoderma affecting many different trees, particularly broadleaves. They cause a white rot, often at the base of the trunk leading to windthrow, although they can also be found higher up the
trunk. Fruiting bodies take the form of shelf- or hoof-like brackets, often brown above and whitish below. They are perennial, can be very hard, and increase in size over several years, sometimes reaching up to two feet in diameter. It can take many years for affected trees to become unsafe.
Honey Fungus (Armillaria species)
Probably the most well-known decay fungus, it also has the widest host range, killing not just trees but many other woody plants. The term ‘honey fungus’ covers a number of species of Armillaria, with some more aggressive than others. Armillaria mellea and Armillaria ostoyae are the most damaging. Honey fungus causes a white rot and principally affects the roots, but it can also spread into the stem base in the later stages of attack. A white sheet of fungal growth below the bark of decaying roots or stem bases is the most diagnostic feature of this disease. Fruiting bodies are
produced in the autumn and are
brown mushrooms with a whitish collar on the stalk just below the cap. However, honey fungus differs from the other decay fungi in that the spores produced by the mushrooms do not play a major role in the spread of the disease. Instead, the fungus spreads through the ground by means of black, string-like structures called bootlaces or rhizomorphs. These can grow several metres in length and can colonise the roots of an adjacent plant if they come into contact with them. Unlike other decay fungi, honey fungus is also perfectly capable of penetrating healthy bark - no wounds have to present. Further information on these and the many other decay fungi can be found in the books ‘Diagnosis of Ill-Health in Trees’ and ‘Principles of Tree Hazard Assessment and Management’, both published by The Stationery Office.
ROT!
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