Xylella fastidiosa, a pathogenic bacterium of rare aggressiveness, represents a major threat to agriculture and horticulture. Capable of infecting more than 400 plant species, it is distinguished by its lack of curative treatment and its rapid spread. This bacterium mobilizes researchers and agricultural professionals to try to stem its ravages and preserve ecosystems.
What is Xylella fastidiosa?
Xylella fastidiosa is a bacterium that settles in the sap-conducting vessels, called xylems . It spreads thanks to piercing-sucking insects (Leafhoppers) that feed on the raw sap. Once installed, it obstructs these vessels, disrupting the water and nutritional supply of the plant . The consequences range from wilting to the death of the host.
Xylella fastidiosa is also responsible for many diseases in different species, including rapid olive dieback disease (CoDiRO) to name just one.
Deadly to plants, this bacterium is harmless to humans and animals. It comes in several subspecies (fastidiosa , multiplex , pauca , sandyi or tashke) , each with host preferences.
Distribution of the bacteria
Originating from the American continents (North and South), Xylella fastidiosa has spread to other regions of the world, particularly Asia and Europe. On the old continent, it was first observed in Puglia, Italy, in 2013 (where it has since caused the destruction of thousands of olive trees), before being detected in Spain, Portugal, Germany, Belgium and the Netherlands.
In France, this bacteria was identified in 2015 , in Corsica and Provence-Alpes-Côte d’Azur, then more recently in Aude and Gard.
Which plants are affected?
Xylella fastidiosa is a threat to a staggering number of plants. More than 400 species are listed as susceptible to this bacterium. It affects agricultural crops as well as ornamental plants and wild species.
In the fields, emblematic trees such as the vine, the olive tree or the almond tree are particularly exposed. Fruit species, such as the plum tree, the peach tree, the fig tree, the apricot tree or the cherry tree , can also be affected. Citrus fruits are also affected. Just like certain fodder plants such as alfalfa are not spared.
As for ornamental plants, oleander is one of the most well-known victims. But other plants, such as lavender, myrtle-leaved milkwort, Italian everlasting and Montpellier rockrose, are also vulnerable.
How do plants get infected?
Xylella fastidiosa is transmitted by piercing-sucking insects (more than 50 are listed) that feed on the sap. These insects carry the bacteria from an infected plant to a healthy plant, acting as true vectors. In Europe, several culprits are involved including:
- Meadow spittlebug (Philaenus spumarius )
- Leafhoppers (Cicadellinae ),
- Aphrophores (Aphrophoridae ),
- Spittlebugs (Cercopidae ).
The leafhopper named Graphocephala atropunctata is a polyphagous species that consumes xylem, an essential element for transporting sap. It is best known as one of the main vehicles of the bacterium Xylella fastidiosa . It attacks Vitis, Rubus, Urtica, Salix, Sambuscus or Artemisia in its native range. But it also feeds on a wide variety of plants. Polyphagy, wide geographical distribution and transmission of X. fastidiosa combine to make Graphocephala atropunctata a permanent and significant threat to vine cultivation. The symptoms caused by this leafhopper are essentially indirect, caused by the bacterium X. fastidiosa. Climatic conditions have caused a resurgence of these pests in recent years.
What are the symptoms and damage of the bacteria Xylella fastidiosa ?
Symptoms caused by Xylella fastidiosa can vary widely depending on the plant affected and the subspecies of the bacteria responsible. Some infected plants show no visible signs (they are said to be asymptomatic), but they still carry the disease and increase the risk of spread. Others, however, suffer serious damage, sometimes fatal.
These symptoms, often not very specific, complicate identification. You might observe:
- Wilting or browning of leaves,
- Leaf burns ,
- Dwarfism in certain species, such as the peach tree .
The bacteria is also responsible for serious illnesses , including:
- Pierce’s disease on the vine,
- Variegated chlorosis of citrus fruits,
- Rapid olive tree desiccation syndrome ( CoDiRO ),
- Coffee leaf blight.
Regulations and preventive measures
Faced with this threat, Xylella fastidiosa is classified as a quarantine organism within the European Union. This classification requires increased vigilance on the part of authorities and professionals. Current regulations provide for regular inspections of susceptible plants, as well as increased surveillance of imports of plants likely to be contaminated. Raising awareness among agricultural stakeholders and gardeners is also essential to slow the spread of the bacteria.
Monitoring and control of Xylella fastidiosa
Controlling Xylella fastidiosa requires a rigorous and multidimensional approach. Rapid identification of infection sites is essential to limit its spread. Infected plants are uprooted and destroyed to reduce reservoirs of contamination.
AGROBIOTOP SOLUTIONS
- Natural solutions to combat leafhoppers (vegetables) that carry the disease against xylella fastidiosa .
- Solutions to activate the plant’s defense system.
- Active and specific ingredients contained in biostimulants formulated by AGROBIOTOP to combat pests and disease.
