Reading my September issue of the RHS Garden magazine I learned that yet another fatal plant disease is looming on the horizon. Xyella fastidiosa, a bacterium that infects the water conducting vessels of plants, has been working its way across Europe since 2013. Symptoms include leaf scorch, wilt, die-back, and death. Of course, quite a lot of other things can lead to the same list of symptoms in plants, and not all plants infected with Xyella show any symptoms at all.
The first manifestation in Europe was in olive trees in Puglia. I'd seen in the papers that something was infecting olive trees in Italy, and felt sorry about it, but Italy seemed comfortingly far away and olive trees seemed quite niche from a UK point of view. Now it turns out that the thing that was attacking olive trees in Italy has also been found in oleander, Polygala, cherries, and almonds, in locations across France, Germany, Spain and the Balearic Islands, and that it is thought to be capable of infecting 359 species (so far and counting) across 75 different families, including hebe, lavender, rosemary, oak, and herbaceous plants as well as shrubs. It has not been found in the UK yet, but what's the hope of it staying out, given our fondness for cheap Dutch plants and Italian specimens?
The rest of the article did not make comforting reading. The UK has regulations in place to keep the disease out of Britain, namely that importers have a responsibility to ensure plants originate from a disease free source, one that has been inspected and confirmed to be disease free. Inspected for signs of a disease that can be symptomless, and whose presence can only be confirmed by specialised laboratory testing. Run it past me how that works, exactly.
There is a Government plan on what to do if Xyella is found in the UK, but that didn't fill me with confidence either. Control measures focus on removal of host plants and control of the insects that spread the disease. Um, it is spread locally by sap sucking insects like common froghoppers. How are we going to control those, by spraying chunks of the Home Counties with DDT? If the infection is thought to have become established the host plants within a 100m radius must be destroyed. I took a bit of time to digest that. A hundred metres could easily span the width of eight or ten suburban gardens and the depth of three roads. Thirty gardens? I tried to imagine DEFRA officials going through them removing every hebe, lavender, floribunda rose, sycamore, bird cherry, native oak, and ivy plant, plus whatever else Xyella can live on. And what would they do with the debris? Burn it in the road in great piles like cow carcasses during the foot and mouth outbreak?
Would the householders get compensation for their ruined gardens? Who would pay for the removal? Who would do it? And who would report a suspected case of Xyella to DEFRA? Most people would quietly dig out their ailing shrub or hire somebody with a chainsaw to come and chop down whatever tree looked poorly and cross their fingers that it was dying of something else, rather than risk bringing down a Government scorched earth policy down on their own garden and their entire street.
Of course post Brexit we could adopt biosecurity measures as strict as Australia's, if we wanted to, apart from the difficulty that unlike in Australia the rest of the European continent is within flying and drifting distance for spores and insects, and lots of people arrive in the UK with vehicles by ferry and train. But we could, if by good luck we manage to evade Xyella until then. I can't see plant health making it to the top of the list of Brexit issues to be addressed in any timescale that would be of any use, though.
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