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What is the Xylella fastidiosa?
It is a bacterium that has a wide spectrum of hosts – after all, causes disease in about 350 species of plants – and it is known that there are five subspecies of this bacterium. the Xylella fastidiosa it was first described in 1987, but the disease that causes the vine (known as Pierce's disease) had already been observed at the end of the nineteenth century in California. This disease can cause great losses in the wine sector.
Until 1994 this bacterium was limited to the American continent, but this year was found in Asia, specifically in Taiwan and Iran, and it appeared for the first time in Europe in 2013 in the Puglia region. He hit several olive trees in a large area and plants of the species Nerium oleander (Oleander) Prunus dulcis (almond) and the genus Quercus. In 2015 it was taken over in France. Now he has arrived in Portugal.
Vine leaf affected by bacteria
Aaron Jacobson / UC Davis
What problems does it cause?
It causes serious damage to olive trees, citrus fruits, vines, fruit trees and other plants, including ornamental plants. The symptoms found in plants vary according to the host, but are generally associated with stress like wilting, burns or even the death of the plant. For example, in the olive groves – which are very vulnerable to these bacteria – it can cause a rapid decline of the aged trees and in the vines it can cause the withering of the leaves and the yellow and red chlorosis. However, many plants may not even show the symptoms of the infection.
How is it transmitted?
the Xylella fastidiosa it is transmitted from one tree to another through the insects belonging to the order Hemiptera, like spittoons, which feed on both the larva and the adult phase. If one of these insects sucks the sap from an infected tree and then turns it into a normal tree, it will eventually infect it. When it reaches the plant, the bacterium begins colonizing the wood, then spreads through the tree and ends up clogging its fluid circulation system. In the case of olive trees, plants even wither from the root to the crown.
Over long distances, the main way of dispersal of this bacterium is through the trade in contaminated plants. However, plant material such as wood, fruit and ornamental foliage have a low risk of transmission. It can also be transferred through grafting between contaminated plant parts and there is some evidence that – even at low risk – can be transmitted through pruning tools on the vine.
Is there a treatment for the "annoying" disease?
Not yet. Therefore, the only way to stop the evolution of the disease is to kill infected trees or avoid contamination through early detection.
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