Downlands Tree Surgery

Bleeding Canker of Horse Chestnut

  We are seeing more and more often Horse chestnut trees in decline. Long splits in the bark, crown and limb dieback and resinous bleeding on the trunk and branches are all too often the symptoms of Bleeding Canker of Horse Chestnut. According to the Forestry Commission this is not new and this type of symptom which was first reported in the 1970s, when the cause was found to be a fungal pathogen known as Phytophthora but in 2002 it was discovered that a completely different pathogen, a bacterium, Pseudomonas syringae pv aesculi, was responsible for the increase in these symptoms appearing on horse chestnut.

 What trees are affected?

• Trees of all ages have been affected by the recent disease upsurge. 
• Young trees with a stem diameter of only 10cm (4 inches) have been found with advanced symptoms. 
• The impact on the environment can be particularly profound when large, mature trees are infected and disfigured by the disease. 

 Management of the disease

• At present there is no chemical treatment currently available to cure or slow the development of bleeding canker.
• If the bleeding lesions become so extensive that the entire trunk is girdled, the tree will inevitably die and have to be removed and disposed of appropriately.
• If major branches are infected and show dieback they should be removed, because recently-dead branches of horse chestnut may be susceptible to sudden fracture and drop as the wood dries out.
• Some trees may even survive for many years as disease progression can be very slow or even cease, and show signs of recovery as vigorous callus development occurs at the margins of wounds created when bark has been killed by the disease.

 However; according to an article in Horticulture Week it is not all doom and gloom; scientists have recently been able to decode the genome of a bacterium causing the canker. The genome sequence will allow scientists to determine which genes might be necessary for infection of a tree host so they can be targeted to manage the disease.

Information from the Forestry Commission 2009 and Horticulture Week 2010.

This disorder of Horse Chestnut is not to be confused with the Horse chestnut leaf miner which causes the leaves to curl and turn brown. That’ll be my next blog!

Beech tree with severe crown dieback through soil compaction

Because we don’t see trees’ roots we often forget how important they are.

The main function of roots are ; anchorage, storage, transportation and water and nutrient absorbsion, if you remove any one or more of these functions the tree will fail.

Through our work we regularly see trees that are dying back from the top of the crown and are requested to reduce the trees’ crown, generally this type of dieback indicates the tree has a root problem and more often it has been caused by compaction of the soil.

Soil compaction means poor soil structure this means root death! Or in the case of a newly planted tree the roots will not be able to grow and penetrate the soil; result a dead tree and a waste of money!  Water will not drain freely and can lead to waterlogging or poaching creating anerobic conditions (no oxygen) and roots will in effect drown. The fine fibreous feeding roots of a trees’ root system extend for many metres beyond the ends of the branches (dripline) and will continually grow and dieback supplying the tree with water, nutrients and OXYGEN from the soil.

Common causes of soil compaction effecting tree health can be; increased/raised soil levels around the base of a tree, even if it is temporary the damage will be done! Piles of stored materials such as stones or a fresh compost heap. Heavy foot traffic or machinery, parked cars and livestock.

Building sites are notorious for soil compaction through use of heavy machinery. If you are having building work done do not let any materials be it soil, scalpings, stone, timber or whatever put under the dripline of your trees! No matter for how shorter time. It will not show in the first or probably second year and everything will appear to be fine but often three to four years down the line the first signs of crown dieback can appear, believe me it will happen!

A tree that is stressed because of soil compaction is more susceptible to root pathogens such as the dreadded Honey Fungus, Meripilus giganteus or Phytopthora

Beech tree with Meripilus giganteum, root damage and soil compaction caused by construction

What can be done?

If you have a tree that is dying back you can try stripping the turf out to the dripline and mulching the area with a WELL COMPOSTED wood chip and leaf litter, the idea is you get the worms to do the hard work for you. They will eat the organic matter, working it into the soil improving  drainage, available nutrients and improving the soil structure.

Soil decompaction, can be carried out with specialist equipment like Terravention that injects a high pressure blast of nitrogen (an inert gas) that fractures the soil structure, a liguid feed can also be added or an Airknife, which will break up the soil structure and you mix in a mulch with the decompacted soil (Very messy).

Pruning of branches should invigorate new growth but this should only be done if the soil issue has been addressed otherwise the tree will only be using its stored energy.

There would be Health and Safety issue and any major deadwood should be removed especially if your tree overhangs a road or footpath to avoid damage to third parties and property.

If you have a tree that you are concerned about call us for more information and advice.