The honey-coloured fruiting bodies of honey fungus (Armillaria spp) (image: Wikimedia Commons)
Honey fungus or Armillaria are a group of parasitic fungi. They attack trees, shrubs and woody perennials, and are one of the most destructive fungal diseases in the UK.
They are also among some of the biggest living organisms in the world, their underground networks often covering many miles and living for up to a thousand years.
It is so successful because, unlike most parasites that rely on keeping their hosts alive in order to extract nutrients, it can kill its host and continue living on the decaying matter for many years. Watch our video on how to diagnose honey fungus
The fungi spread by long reddish brown root-like rhizomorphs that live close to the surface of the soil.
They attach themselves to the root collar of woody plants, killing off the root systems leaving the host unable to absorb nutrients and water. You can watch our video on how to diagnose honey fungus