Friday, 3 July 2009

Stinky solution for bloody canker


Garlic sprays are popular for gardeners wishing to use less refined products to control their garden pests. Garlic is mixed with water - sometimes with chilli, onions or soap - and applied to leaves to control unwanted visitors such as aphids.

It's always nice when home-grown remedies such as this receive a tick from scientists. As someone of sceptical disposition I always seek extraordinary evidence for extraordinary claims, but garlic is a known antibacterial agent so it's no wonder small bugs don't like it - although technically it could help protect them from any irritating bacterial diseases and make leaf-munching more pleasant!

In a report in the latest issue (July 2009) of the The Garden, the magazine of the Royal Horticultural Society, it seems that giving garlic to your plant intravenously may also be good for its health. 'Bleeding canker' is a foul-sounding name for a nasty disease of Horse Chestnuts (Aesculus hipposcastanum). Since the 1970s, England has lost some of its majestic old Horse Chestnuts from this bacterial pathogen. (Although bleeding cankor has sometimes been attributed to the fungal-like Phythophthora, this recent epidemic seems to be bacterial.)

The 'blood' is the blackened gum that oozes from the bark of diseased trees. If the canker makes it all the way around the tree, it usually dies. The article quotes Forestry Commission statistics of up to 3000 infected Horse Chestnuts being felled for public safety. '...trees start to bleed one year and are dead the next...'

A new treatment from the Netherlands would be a breadth of fresh air, except that the leaves end up smelling strongly of garlic! But the good news is that an injection of allicin, extracted from garlic, has helped trees recover within a year. The garlic in the leaves isn't really a problem either as it helps to repel moths that don't help the problem by defoliating the Horse Chestnuts.

Until now the recommended treatment was to do nothing. Cutting off infected limbs can create new entry points for the bacterium and will help spread the disease. And no antibacterial chemicals have been available for use in home or amenity gardens.

It's worth the odd whiff of garlic if you can save a tree.

And the picture? It's a Dracula orchid in our Tropical Centre...sorry...

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