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A Potential Cure on the Horizon for Horse Chestnut Bleeding Canker

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Bleeding Canker in Horse Chestnut trees is caused by the bacteria Pseudomonas syringae pv. aesculi, and has only recently been recorded in Europe.

Bleeding Canker is a vascular disease, which appears to be spread through ground water from tree to tree and the control of the disease has, up until recently, been considered to be impossible. This is because the bacteria, once in a host, will multiply in the comfortable environment of the cambial area which surrounds the whole surface of the tree beneath its bark from the major roots up to the finer branches. Consequently, any combating anti bacterial agent must be able to travel around the tree, kill the bacteria, have no detrimental effects upon the tree and importantly have no harmful effect upon any organisms which live in, feed off or rely upon the tree in any way.

Conventional treatment methods such as spraying, root injection or removal of bleeding wounds have been found to be ineffective and harmful, often resulting in more damage to the tree. JCA have obtained experimental approval to test a new product which shows considerable promise.

A Badly Affected Stem
Fig 1: A badly affected stem
An old treatment point
Fig 2: An old treatment point

JCA Limited, in partnership with Allicin Tree Care in The Netherlands, have developed a new product, which, when introduced into the tree using a unique infusion method provides a breakthrough in the fight against Bleeding Canker in Horse Chestnut trees with applications for many other tree and shrub diseases. JCA Limited started UK tests in Summer 2009 and will continue throughout 2010, after extensive tests in The Netherlands which produced remarkably encouraging results.

Allicin is a substance which occurs naturally and is one of nature’s most effective anti fungal, anti bacterial and anti viral agents. It has been known to man for centuries but until recently has been impossible to obtain in sufficient quantity or at a sufficient strength to use in anything other than human medicine. Our partners have obtained a worldwide patent on a method of commercially producing and stabilizing Allicin, in sufficient quantities and at a significant strength, allowing it to be used in Horticulture and Arboriculture.

Allicin is manufactured from natural plant material (Allium sativum) which is grown under European GAP (Good Agricultural Practice) conditions. It is produced without the use of chemicals, is completely biodegradable and is safe for humans and the environment. Production is carried out under BS and ISO standards 9001:2000. In addition, it has been tested by the internationally respected organisation TNO, Organisation for Applied Scientific Research, in The Netherlands, whose tests proved that, when using the correct concentration, Pseudomonas syringae pv. aesculi, is destroyed. Further tests by the Botanic Diseases Department of the Dutch Ministry for Agriculture, Nature and Food Quality in Wageningen, The Netherlands, verify these results.

A tree being treated
Fig 3: A tree being treated
Revived tree
Fig 4: Infusion equipment
Fig 5: A revived tree

In order to obtain the best results, treatment with Allicin is required as early as possible after the tree has been diagnosed as being infected. Using the tree infusion system, the solution is introduced into the cambium layer of the tree around the stem. Root pressure and capillary action ensure the distribution of Allicin around the tree via its vascular system. The size, vigour and condition of each tree help to calculate the volume and strength of Allicin required. The unique infusion system is designed for this purpose. Field trials have proven that the use of Allicin by this method gives the desired result.

In addition to its anti bacterial effect, Allicin has fungicidal and anti viral qualities. After Pseudomonas Syringae pv. Aesculi infection, a tree’s resistance to pathogens diminishes allowing fungi to develop in the tree. These fungi are also killed by Allicin.

A Welcome Side Effect

In tests carried out in The Netherlands, a welcome side effect was noted which is also of considerable benefit to the Horse Chestnut. A control avenue of Horse Chestnut were left untreated whilst a parallel avenue of Horse Chestnuts were all treated. Apart from the desired effect of a general recovery in the treated trees, it was noted that they remained by and large, unaffected by leaf miner Cameraria ohridella and completely foliated.

In contrast, the control avenue was almost completely defoliated by mid September and heavily infested with leaf miner. It appears that as the Allicin travels throughout the tree’s vascular system, it taints the foliage with the odour and taste of Allium sativum which the leaf miner finds not to be to its taste. Proof of this transfer throughout the trees system can be obtained by breaking off a leaf from the tree a week or so after treatment. If the leaf is crushed, a distinct Garlic smell can be detected.

Treated avenue
Fig 6: A treated avenue of Horse Chestnut trees
Control avenue
Fig 7: An untreated avenue of Horse Chestnut trees

The avenue of Horse Chestnut trees in Fig. 6 was treated with Allicin.

The control avenue shown in Fig. 7 was not treated. Both photographs were taken on the same day on adjacent avenues.

Clearly, Fig. 7 shows trees badly infested with leaf miner.

Horse Chestnut trees, whilst an introduced species, have become an immensely important amenity tree in the UK and they hold a special place in the hearts of the nation because of their fruit, the Conker.

Whilst the solution itself is quite expensive, treatment with Allicin is cost effective when compared to the high financial cost of mass tree removal both in environmental terms and financially.

Any tree owner interested in becoming involved with the tests should contact JCA Limited at the address below, or via email at info@jcaac.com.

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