The olive killer, xylella, has reached Spanish ground, specifically the Balearics and it can´t be long before it reaches the mainland. Sadly another ‘plague’ that could destroy a whole way of life, a huge industry and the wonderful look of our countryside.
Xylella is a bacteria; a silent but serial killer. And it doesn´t only affect olives, though this is the most impacted host plant to date. It is known to attack some 300 species of trees and shrubs including sweet orange, almonds, cherry, vine and many ornamentals such as oleander, polygala, Spanish broom, periwinkle and mimosa and this diversity is, of course, where the real problem lies.
Across the stony heel of Italy, an area called Puglia has been decimated by the killer since 2013 when it was first detected. In this densely wooded area of some 10 million olive trees, it is reckoned that up to one million of them have been cut down, many of them venerable trees. The Italians resisted the felling order from Brussels which was issued in an attempt to stop the spread of the disease; pictures of farmers weeping whilst their ancient olive groves, their heritage and livelihood, were bulldozed and burnt were heart-wrenching.
The war between growers and politicians raged as the fires burned. It nowappe ars that such drastic measures may have been a little heavy handed as newest research seems to indicate that whilst some varieties of olive are more vulnerable, some are immune and that it does not easily infect other species. However, all this research is in its early stages and the true picture is, largely, still to come. In Spain, lack of funding has prevented much investigation so it is not yet known whether our local varieties of olives are particularly vulnerable.
The bacteria was first noted in Mallorca in Porto Cristo in October 2016 and is now in Ibiza too. Both affected areas have just been put under quarantine and exportation of plants or plant material from the islands is now totally prohibited. (Please take note if you are travelling – no sneaky cuttings in suitcases because you just never know!) On Mallorca there are 71 infected trees and on Ibiza 21. To date all are olives, cherries and almonds but ornamentals could also be infected and not yet showing signs.
Some 2000 plants in the immediate area have been destroyed as a precautionary measure and to prevent spread.
The bacteria is spread by a sucking insect known as the meadow spittlebug, philaenus spumarius. This little insect, some 5 to 7mm long is the vector.
They are variable in colour, ranging through pale beige, brown to black, sometimes with markings. They can only fly up to 100m, hence the general order for all susceptible plants within a 100m radius to be felled, sick or healthy, as a buffer zone and in an attempt to stop the spread into other areas and other countries.
Four subspecies of xylella have been identified – fastidiosa, multiplex, pauca and sandyi. The main subspecies in Italy is x. pauca though x.multiplex has also been reported. In Mallorca the first cases have been caused by x. fastidiosa. This seems to indicate that it has not spread from Italy. Furthermore, the bacteria in Spain is genetically different to the Italian strain which has been tested and found to match that found in Costa Rica. Bearing in mind that the bacteria has so many possible host plants and symptoms cannot be detected in the early stages, it is difficult to say, with certainty, where it arrives from.
Once the bacteria attacks, death is relatively rapid though large trees can take a few years to die. It slowly restricts water flow from the roots to the plant, a suffocating strangulation and slow death. The first noticeable symptoms are leaf scorch around the margins, a reddening and curling of leaves followed by desiccation, dieback and bare-looking branches but
these symptoms can easily be muddled with other diseases/environmental conditions. Early diagnosis, massive pruning and burning of the prunings may help but the difficulty is knowing if you have cut out the problem. If not, you are leaving the source to spread to other plants.
This bacteria isn´t new; it was first detected in California in 1880 and has badly affected grapevines there through the years. In Brazil, it is orange trees that are attacked. We have lived with it for well over a century and it is not entirely clear why, this time, the effects have been so massive.
There is no cure but, in the U.S. and Brazil, there has been some success with genetically modified plants. It works on grapevines and ongoing work is in place but in Europe, of course, the regulations on G.M.O.’s are completely different. In Spain the battle will be centred around the search for a virus that will kill the bacteria and control/elimination of the insect. It is essential to try and limit the outbreak to the Spanish islands. The worst case scenario will bring the battlefields of Italy to mainland Spain.
It is, literally, on our doorstep. With the value of the Spanish olive oil market at 1,800 million euro annually, and rising, and millions of livelihoods at risk, the battle and consequences will be enormous.
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