Friday, 15 January 2010

Garlic Futures....

Garlic is being used to treat Horse Chestnut diseases. In the summer of 2009 I read this news announcement in the RHS magazine The Garden and it seemed to be so profoundly surreal I found it intriguing. It is such a hippy concept really! However it is true and it does appear from the trials published on the internet as though some very profound results have been achieved in treating two extreme problems that occur in Horse Chestnuts.

The major problem that triggered the research, which has until last year been carried out in The Netherlands, is a fairly new to Europe but invasive disease called Bleeding Canker. This is a disease caused by bacteria that breed in areas of the trees that traditional treatments cannot reach effectively. The bacteria is called Pseudomonas syringae pv. aesculi. More information is available on the website for the UK partners with the Dutch company Allicin Treecare, JCA Limited: where they give details of techniques and photographs of the process. Their product called Allicin is pumped into the lower trunk of the tree and capillary action carries it to the rest of the tree, including the leaves, which apparently take on a garlicky aroma.

Garlic is used for treating humans for a range of fungal conditions and for blood purification and garlic capsules are widely available. It is interesting to cross-refer this post to an earlier one on the methane produced by cows and sheep here, since garlic is to be used as part of the process to curb their emissions!

The second disease that appears to be vulnerable to the Allicin treatment is the more widespread leaf miner (Cameraria ohridella). This is very interesting as it ties in a bit with the use of garlic in cooking which I have personally noticed discourages house-flies. Trees that have had the Allicin treatment in areas suffering from leaf miner attack have kept their leaves, whereas neighbouring trees have lost almost all of their leaves. The photograph that I have used shows leaf miner damage in street trees in Gdansk, Poland.

In Elliot, R & de Paoli, C Kitchen Pharmacy (1991) the authors say that the antiseptic action of garlic is effective against viruses, fungi and bacteria and that Galen called garlic the 'great panacea', which seems to be proving very true at the moment!

While all of this seems to be very positive and is very promising for the look of the greater trees in the landscape, there is a little boding disquiet in my own mind. Trees are very far from a monoculture. The oak tree is the obvious example to use, where whole communities live in the ecosystem of roots to branches. It is already obvious that invasive insects are not keen on the garlic. Is it possible that beneficial or benign insects might also be affronted? Might other organisms also be disturbed? Lichens, the journalists of air pollution, are formed through a symbiotic relationship of fungus and alga that become 'lichenised'. Garlic is being used specifically for its anti-fungal properties. I would like to see some interest taken in the lichens on the treated trees, maybe they could be reporters for the habitat implications? In the UK, Horse Chestnut is not a key substrate for lichens, but it is far from improbable that this technique will be used for other trees under other circumstances and could in future be taken up in tree nurseries. It is a brilliant technique, but the wider implications do need to be considered while it is still young. At the moment it is far from cheap to innoculate a tree. This may not always be the case and as responsible adults it may be important to weigh up several pros against some cons.


  1. As Dutch Elm Disease is a fungus, admittedly borne by beetles, could it respond to garlic treatment? Elm is a very key lichen substrate, and the lichens dependent on it have suffered catastrophic decline, and in some cases national extinction.

  2. We eat a lot of roast garlic and pepers, and sometimes with sweet chestnuts as well. Maybe the trees would like their garlic cooked this way!