Honey Fungus Treatment

Armillaria mellea – Honey Fungus – Armillaria Root Rot

Honey FungusHoney Fungus is usually detected in the Autumn when toadstools appear around dead and dying plants.  They are one of the most prevalent root diseases, parasitizing many plant species and infecting neighboring plants through the soil.

Although these fungi can become a serious disease for gardeners, without them the Earth would probably be covered in dead trees. As a wood-decaying fungus it breaks down dead trees returning nutrients to the soil.


Making a diagnosis isn’t easy as plants can die for all sorts of reasons, so gardeners shouldn’t be too alarmed if they see a toadstool in their garden during autumn – it is not necessarily honey fungus and most toadstools are harmless.  Symptoms to look for are:

  • Mass flowering/fruiting before death
  • Yellowish toadstools arising between Jul and December
  • Sappy gum exuding from the base of infected trees
  • White mycelium (fungus roots) under bark
  • Black bootlaces (rhizomorphs) in soil and sometimes under bark
  • Wet or slimy roots that may also smell ‘mushroomy’
  • Herbaceous perennials die back, leaves may wilt or fail to appear in spring

How did I get it in my garden?

Honey Fungus in the garden originates from dead stumps or the buried roots from trees that have died or been felled some years before. Unfortunately when the tree was removed (maybe sawn off across the base rather than pulled over) the roots left behind are the food supply for the disease. Once you have this situation where you have inoculated roots underground it is very hard to remedy, as removal of these roots is extremely difficult.

So what’s the remedy?

Dig out infected plants taking care not to drop infected soil or plant material in other areas of the garden and spreading the problem.  Where the source of infection is precisely located, its spread may be inhibited by inserting a vertical barrier of heavy polythene or butyl rubber pond liner material to a depth of about 30cm (12in).

Always ensure your plants are well fed, watered and mulched as healthy plants are more able to withstand fungal attack.

If possible, when honey fungus has been detected in the garden, replant with resistant species – it is likely that some fungal spores will remain in the soil and re-infect new planting.  The tables below lists common plants that have some resistance and those that are particularly susceptible.

Plants that have shown to be relatively resistant to honey fungus include:
  • Acer negundo (but not other Acer species)
  • Actinidia
  • Abutilon
  • Bamboos
  • Carpenteria
  • Catalpa (Indian bean tree)
  • Celastrus
  • Ceratostigma
  • Cercis
  • Chaenomeles (Japanese quince)
  • Clematis
  • Cotinus (smoke bush)
  • Fothergilla
  • Hebe
  • Juglans nigra (but not Juglans regia)
  • Kerria
  • Passiflora (passion flower)
  • Phlomis
  • Pieris
  • Pittosporum
  • Quercus (oak)
  • Rhus (sumach)
  • Romneya
  • Sarcococca
  • Tamarix
  • Taxus (yew)
Plants that are particularly susceptible to honey fungus include:
  • Betula (birch)
  • Cedrus
  • Cotoneaster
  • Forsythia
  • Hydrangea
  • Ligustrum (privet)
  • Malus (apples and crabs)
  • Paeonia
  • Prunus (apricots, cherries, peaches, plums)
  • Rhododendron
  • Ribes (currants)
  • Rosa (rose)
  • Salix (willows)
  • Syringa (lilac)
  • Viburnum
  • Wisteria

Information courtesy of The Scotts Company Ltd.

To see a full list of all our handy fact sheets click here