Honey Fungus: What is it and what can you do about it?

Honey Fungus: What is it and what can you do about it?

Honey fungus is the common collective name given to a number of different species of fungi (Armillaria) that attack and kill the roots of woody and perennial plants and is the most destructive of all fungal disease in the UK.

The fungus spreads underground by direct contact between the roots of infected and healthy plants and also by means of black, root-like structures called rhizomorphs, which also spread from infected roots through the soil. Rhizomorphs can grow as deep as 45cm or more and spread at the rate of 1 metre per year, often attacking plants up to 30m away from the source.

How to spot Honey Fungus

The most conclusive indication of Honey Fungus is the presence of white fungal growth beneath the bark on roots and the collar portion of a dead or dying tree. When you peel back a section of the bark from the lower trunk or upper roots, you will find white or cream paper-like sheets sandwiched between the dead bark and underlying wood which have a strong mushroom smell.

Other symptoms include:

• The upper parts of the shrub or tree dying. This is sometimes over a period of several years or can be a sudden onset during hot weather which can mean a failure of the root system.
• The tree or shrub will have smaller and paler leaves than normal
• Absence of a flowering season or sometimes a really heavy flowering and crop of fruit (usually occurring just before death)
• Cracking or bleeding of the bark at the base of the stem
• Yellowy, golden mushrooms are produced in Autumn at the base of an infected tree (subject to suitable conditions).

How can I treat it?

Unfortunately, there is no chemical treatment available to control this disease and sadly the only effective treatment is to excavate the infected roots and stump and destroy them through burning or taking it to a landfill site. Without the infected material to feed on, the rhizomorphs are unable to continue to grow.

To stop honey fungus spreading to unaffected areas, you will need to take steps to block the passage of the rhizomorphs by using a heavy duty plastic sheet or section of pond liner that you can place vertically to a depth of at least 45cm with a few centimetres protruding above ground too.

The spread of rhizomorphs can also be limited by regular, deep cultivation of the soil surrounding the infected source.

Are there some trees and shrubs that are more susceptible than others?

The most susceptible trees and shrubs include: apples, crab apples, walnut, willow, wisteria, cotoneaster, rhododendron, roses and many conifers, including pine, cypress and thuja.

If you take the option to remove the diseased shrubs or trees you must remove the roots as far as possible, replacing the infected soil from around the diseased plant.

Where possible have any large stumps removed from the garden.

When considering replanting be sure to do so at least 12 months after the removal of the affected tree or shrub and stick to plants known to be resistant such as oak, ash, beech, yew, clematis, laurel or mahonia.

If you suspect that you may have trees affected by Honey Fungus then you need to act sooner rather than later to stop the potential spread of the disease to nearby healthy plants and shrubs.

Our experienced team are happy to take a look at any problem trees and make recommendations on treatment or removal (if necessary). Call us today on 01473 635193.

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