For millennia, garlic, the ‘bulb’ of Allium sativum, has been used medicinally to help make humans better. Whilst many of these so-called ‘cures’ may be more fanciful than factually accurate, evidence-based medicine, there are studies that attest to the effectiveness of garlic or extracts thereof and therefrom against a range of human health-compromising bacteria and fungi (e.g. studies by Giles Elsom et al., Simon Woods-Panzaru et al. and Daniel Tagoe et al.). Indeed, so commonplace have such ideas become that garlic can be used as an educational tool investigating the anti-microbial effects of plant extracts. So much for humans: Is this relevant to looking after the health of, say, trees? Well, apparently so. In the battle against fungal diseases of trees, garlic has been mobilised with some success in Northamptonshire (a county in the east Midlands of the UK). Jonathan Cocking (Managing Director of Arboricultural & Ecological Consultants, JCA Ltd), whose company hold an ‘experimental government licence’ to engage in this work, use an allicin*-based solution administered directly to the base of trees. The solution is injected into an infected tree through eight pipes (the ‘octopus’ connection…) and transported throughout the tree via the transpiration stream. Apparently, ‘the moment the active agent starts to encounter the disease, it destroys it’, BBC Environment Correspondent Claire Marshall explains. Although details of the formula used are not forthcoming, it apparently uses organically-grown cloves from Wales, and somehow the allicin involved is stable for up to one year (rather than the usual 5–10 minutes’ lifespan of the molecule(!)). According to JCA’s website, their ‘Allicin/Conquer Project’ was started in 2009, and so far has had success against such fungus/oomycete infections as Bleeding Canker of Horse Chestnut, Sudden Oak Death, Acute Oak Decline and Chalara dieback of ash. Although seemingly effective, widespread use of this treatment is considered impractical and expensive, and is unlikely to be used except to save trees of ‘historic or sentimental value’. It’s always reassuring to know that it’s still down to ‘value’(and that so-predictable human obsession with money/profit, etc…) as to which trees are allowed to die and which are worthy of being saved (in the UK, at least; I’m sure elsewhere in the world a much more enlightened attitude to saving trees prevails…). Anyway, let’s just hope the 10 finalists in England’s ‘Tree of the Year’ competition are in that ‘sufficiently worthy’ category should they succumb to some life-threatening infection, whether fungal or oomycete (or viral or bacterial or mycoplasmal or prionic, or …)!
* Allicin, ‘garlic’s defence mechanism against attacks by pests’.[I expect it’s been considered (and ruled out), but, mindful of reports of viruses accompanying imported garlic and the fact that plants are attacked by a wide range of virus pathogens, one trusts that the Welsh allicin, as organic as it no doubt is, is sourced from virus-free garlic and doesn’t pose a virus-infection threat to the trees into which it is injected… – Ed.]