Identifying and Preventing Honey Fungus

honey fungus

Honey fungus, bootlace fungus or honey agaric (Armillaria mellea) call it what you will, is becoming a serious and widespread disease. As more and more houses are being built and gardens made, often on the site of old hedges, cleared shrubland or where trees have been removed, so the menace increases. Scarcely a day passes without a report of part of a hedge, sometimes even whole hedges or well-established shrubs collapsing and dying without apparent reason.

Like most other fungi it attacks the weaker plants or those which have been damaged or debilitated by being planted in badly-drained, waterlogged or otherwise unsuitable soil. The best safeguard is prevention, but unfortunately few amateur gardeners, particularly  beginners, realise the potential danger in the remnants of old roots, old wood chips and debris from hedges and woods. Often, too, this is masked by the builder spreading a load of soil over the original half-cleared debris. It may take some years before the insidious bootlace-like growths wriggle through the soil in search of living victims.

What often happens is that this fungus becomes established on old tree stumps in bits of broken root and gradually spreads through the soil until it finds the damaged, dying or even dead roots of badly planted trees or hedging materials. It then attacks and spreads to the living tissue. I cannot think of any other disease which spreads so insidiously, is such a killer and is so difficult to treat. This is mainly due, not only to its invasive nature, but also to the fact that the disease can spread from mushroom-like fruiting bodies which appear in late summer. These take the form of honey-coloured caps with brown scales and long yellowish stems. From these will be liberated spores which will infect other dead stumps and debris. From the source of infection long shiny black cord-like strands are sent out, like something out of science fiction.

Killing and Preventing Honey Fungus

Any shrub or portion of hedge which mysteriously dies should be carefully dug up and promptly burned, even if it means lighting a fire especially for the purpose. It is of little use replanting, as the fungus can remain in the soil for many years and will attack all dead debris and be passed on to living tissue. It does not discriminate but seems to attack almost anything. However, it has a preference for privet, flowering currant and rhododendrons. It will attack herbaceous plants too, even going for rhubarb and daffodils, but as a rule these are only attacked on waterlogged soil.

The method of clearing the soil is laborious and difficult and the only way that I have been able to master it is in the case of a hedge or individual tree by taking out the soil to a depth of 2 ft and twice the width of the root area. To prevent re-infection polythene should be spread on either side of the trench or hole and the top soil is placed on one side and the sub-soil on the other. Take care not to walk about any more than can be helped during this operation. After the whole of the soil has been taken out, prepare formaldehyde or Bray’s emulsion at the dilution of one part chemical to thirty parts water. Throw 3 in of soil back into the trench and soak this with the solution. Continue putting in the layers and soaking them until the job is completed.

There may be other chemicals available which will do the job, but frankly I am not 100%sure of them. I have used Jeyes fluid at the same dilution for this purpose and obtained partial control the first time of application as it changed the character of the growths. These became fanlike and were killed on the second application. Certainly no further planting should take place for at least another season even after treatment. The best preventative is to pick up every scrap of wood chip, root or old stump that it is possible to fork up and rake out.  Never plant in solid clay or waterlogged soil and always try to keep the shrubs growing actively. If you follow this advice you will go a long way to warding off attacks.

28. September 2010 by Dave Pinkney
Categories: Garden Management, Weed Control | Tags: | Comments Off on Identifying and Preventing Honey Fungus


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