Treating the spread of 'Honey Fungus'
A client of Beaufort Landscapes was recently surprised to discover a large clump of toadstools in their back garden. Having been informed of a local outbreak of Honey Fungus, part of the Armillaria genus, that surprise and intrigue quickly turned to shock and fear such is the deadly and destructive reputation this organism has within in the horticultural world. Indeed, this parasitic fungi disease is known to colonise and kill a variety of trees and shrubs, sometimes at an alarming rate and scale (it is widely acknowledged as the largest living organism on Earth with an area of Oregon, USA containing a specific honey fungus measuring 2.4 miles in diameter!). On closer inspection the specimen turned out to be nothing more than a harmless yet inedible relative called the Sulphur Tuft (see image below), however, how does one establish whether their own garden has been effected by this notoriously difficult fungus to diagnose and what treatments are there to halt further infection.
Symptoms to look out for
Primary symptoms include wilting foliage in the spring of the most susceptible plants including apples, lilac, willow, wisteria, rhododendrons, roses, pines, plums and cherries to name a few. This is caused by the fungi's vegetative structure called mycelium (white strands of fungal growth smelling of mushrooms) interrupting the plant's uptake of water. Foliage may subsequently turn yellow and eventually lead to death of the effected plant. Similarly, fruits may quickly become discoloured and wrinkled in appearance.
Another tell-tale sign of Honey Fungus is the presence of black straps or bootlaces present under the bark or in the soil at the base of an infected woody plant or tree. These straps are called rhizomorphs and act as the fungi's main body, similar to that of a plant's root system.
Finally, in autumn clumps of light brown/yellow toadstools (not dissimilar to the appearance of said Sulphur Tuft) may be seen growing at the base of a plants stem. It's worth noting that although toadstools are only seen for a brief period of the year, the life cycle of the fungal disease is present year round.
There is currently no chemical substance available for the control of honey fungus although we would recommend a couple of simple measures to help prevent the spread of the disease. These include removing and destroying and preferably burning infected plants, especially roots and stumps. For all larger stumps, dig a trench around an infected tree to the depth of 0.7m and this will restrict the development of rhizomorphs spreading.
Planting less susceptible species can also work and we would suggest the likes of Clemantis, Ash, Yew, Berberis, Carpinus, Mahonia as a starting point. If you are determined to grow more vulnerable cultivars one solution Beaufort Landscapes implemented recently is the use of containerised pots lowered into a garden plot.
Finally, when dealing with problem gardens make sure all tools used for removing infected material is sterilised after every use.
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