The bacterial pathogen Xylella fastidiosa causes plant disease and can be hosted by approximately 600 plant species. Since its first appearance in Europe in Italy back in 2013, Xylella fastidiosa symptoms have been becoming more apparent and wide-spread throughout Europe. To the untrained eye, mild symptoms of the Xylella infection often go undetected, allowing the disease to spread further. Therefore, it is of the utmost importance to detect these symptoms as early as possible, in order to prevent Xylella from spreading.
If your plants are showing initial symptoms of plant disease such as scorching or wilting, take a look at this list of the 9 Xylella fastidiosa symptoms. It could be possible that your plant has Xylella and you didn’t even know it!
Xylella fastidiosa symptoms
Since 2013, Xylella fastidiosa has been spreading at an unprecedented rate throughout southern Europe and the Mediterranean Region. In some regions, certain plant species have reached a point of no-return as regards controlling the spread of Xylella fastidiosa. Thousands of plants, most notably olive orchards, in regions such as Puglia (Italy) showcase the most severe Xylella fastidiosa symptoms.
In many cases, symptoms of Xylella resemble those caused by drought or frost damage. Above all, those symptoms become more apparent in the summer and autumn months or over longer dry periods.
Before you read about the 9 most common Xylella fastidiosa symptoms, take a look at what causes Xylella in order to understand how Xylella spreads across different plant species.
What causes Xylella?
Xylella fastidiosa is a dangerous bacterial plant pathogen which is transmitted by Xylem feeding insects, namely, spittlebugs. The bacterium, transmitted via the insect vector, colonizes the Xylem vessels of plants. Xylem vessels are responsible for transporting water and nutrient supply from the root of the plant to the leaves and flowers. Hence, when the plant gets infected, Xylella begins to block nutrient and water supply within the Xylem vessels and, as a result, a series of Xylella fastidiosa symptoms emerge. These symptoms can severely damage the plant or destroy it completely.
Which plants can catch Xylella fastidiosa?
There are roughly 600 species of plants, which can host Xylella fastidiosa. Xylella can be found in the most common plants in your garden. For instance, Xylella fastidiosa can be found in:
- stone fruit – olives, almonds, cherries, etc.
- ornamental plans – lavender, oleander, milkwort, rosemary, etc.
- crop plants – grapevine, blueberry, plums, citrus trees, etc.
- native trees – ash, elm, oak, etc.
Xylella plant host list
In order to be entirely sure that your plant isn’t at risk of being infected by Xylella, click here to view the entire Xylella plant host list. (Source: EFSA, April 2020).
9 Xylella fastidiosa symptoms you should know about!
1. Scorching
Leaf scorching, otherwise known as leaf burn or sun scorch, is the browning of the plant tissue. The Xylem vessels of the plant darken, which may lead to either wilting or the abscission (dropping off) of the leaf. Take care if you see that your plant is showcasing signs of scorching. It could be the beginning of many more symptoms to come.
2. Discolouration
Leaf discolouration is one of the most common and overlooked Xylella fastidiosa symptoms. The leaves turn a yellow to brownish colour. When this happens, it means that the leaves are not receiving the appropriate nutrient and water supply. Oftentimes, these symptoms are confused with dehydration, especially in the summer months.
3. Stunting
Stunting describes a plant which has dwarfing or lack of growth caused by a plant disease. Stunting may not be apparent for many months after your plant has been infected with Xylella. If you discover that your plant is showcasing symptoms of stunting, start looking for other Xylella fastidiosa symptoms.
4. Wilting
Similarly to discolouration, wilting is another symptom of Xylella fastidiosa. Wilting is a result of diminished water in the cells which leads to loss of rigidity and vigour. Above all, when wilting occurs, it reduces your plant’s ability to grow, thus leading to stunting.
5. Shrivelled fruit
6. Premature leaf abscission
Leaf abscission leads to bare petioles. Basically, it means that the plant drops the leaf prematurely, making the plant look bare. It is argued that leaf abscission is actually the plant’s defence mechanism against dangerous pests. If you see that your plant is losing its leaves, it could be the case that it has Xylella!
7. Premature fruit abscission
8. Dieback
Dieback is a condition where the branches of the plant die from the tip inward. This one of the most common Xylella fastidiosa symptoms in plants.
9. Plant death
Of course, plant death is the worst-case scenario. Unfortunately, it is not an unrealistic one: this has been the case already in the most severely affected regions of Italy and Spain.
Xylella fastidiosa symptoms on olive trees
On olive trees, you can find any of these 9 Xylella fastidiosa symptoms. However, the most common are abscission of leaves and fruit, scorching, dieback and stunting. Symptoms often begin with dieback of the upper branches.
These symptoms of dieback spread from the crown throughout the olive tree, which usually takes a couple of months. This process is also known as flagging. As a result, the tree begins to look unhealthy and scorched.
Xylella fastidiosa in olive trees has been catastrophic: thousands of acres of olive groves with cultural heritage have been lost as a result of Xylella.
What to do if my plant has Xylella?
Unfortunately, there is no cure for Xylella fastidiosa symptoms. There are only preventative measures one can take to reduce the risk of spreading the disease further. In light of increasing Xylella outbreaks in Europe, scientific communities along with authorities are leading research to find a solution against Xylella.
For instance, the BIOVEXO project is an EU-funded project which aims to establish novel biopesticides for curative and preventative purposes against Xylella fastidiosa and its vectors. Check out the latest insights on the research behind BIOVEXO here.
Does your plant have Xylella? Which Xylella fastidiosa symptoms is your plant experiencing the most? Let us know in the comments section below. Don’t forget to mention the species of plant, symptom and your location.
The BIOVEXO project has received funding from the Bio Based Industries Joint Undertaking (JU) under grant agreement No 887281. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and the Bio Based Industries Consortium.
To learn more about the BIOVEXO project and the research plan, click here.
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