What is it and what are the symptoms of verticillium wilt of the olive tree?

verticillium wilt of olive

Have you ever heard of olive verticillium wilt? It is a fungal disease which, as its name suggests, affects olive trees.

Also known as “withering” or “wilting”, this disease is quite serious and that is why at Jardinería ON we want you to know as much as possible about it so that, if you have olive trees, you can prevent it, detect it and try to save your trees.


What is verticillium wilt of olive

field of olive trees

Verticillium wilt is a serious fungal disease that affects olive trees. It is caused by fungus Verticillium dahliae, which spreads through the soil and can infect the roots of the tree. For this reason, when an olive tree is affected by it, the others around it are in danger because it is easily transmitted through the soil (with irrigation, for example).

Once the fungus infects the tree’s vascular system, it spreads throughout the plant and can cause wilting, yellowing of leaves, defoliation and eventual death of the tree.

You should be aware that verticillium wilt can affect olive trees of all ages, although young trees are more susceptible to the disease. It can also affect other plants and crops, including tomatoes, peppers, potatoes, strawberries, and vines. So, although it has a name related to the olive tree, there are actually many others that can be damaged by this same fungus.

This disease is spread by spores of the fungus present in the soil and can survive for many years. Infection usually occurs through small wounds in the roots of the tree. This can be caused by factors such as water stress, mechanical damage, improper pruning and exposure to extreme temperatures.

Symptoms of verticillium wilt of the olive tree

olive trunk

Now that you know a little more about the disease, and especially how it is generated and what it can attack, it is time to know the symptoms. These can vary depending on the severity of the infection, but in general those that affect almost all olive trees when the disease is detected are:

  • Wilting: The leaf of the olive tree with verticillium wilt wilts and dries up, but not necessarily evenly. Indeed, spots may appear that extend over all the leaves to the point of causing them to wither completely.
  • Yellowing of leaves: Leaves may turn yellow before drying. It’s possible that, if you see this, the first thing you think of is that it needs more water. But it can also happen when the leaves fall (and then it’s harder to notice if you’re not aware of the tree).
  • Leaf loss: The tree begins to lose its leaves prematurely, even before the end of the growing season.
  • Defoliation: As the disease progresses, the tree loses more and more leaves, which can lead to massive defoliation and reduced olive yield.
  • Death of the branches: We refer here to the fact that, in addition to losing the leaves, the branches can also dry out and die irretrievably.
  • Lesions on the bark: In some cases, lesions can be observed on the bark of the trunk and branches. These are signals that indicate there is a problem internally with the tree.

Keep in mind that the fungus attacks from the roots, so it’s an internal attack that can take you down the tree (and sometimes everything around it) in a matter of weeks. In addition, as we have already told you, it can happen that the soil remains affected and that everything you plant there follows the same path because the fungus is still active in the soil.

Possible treatments for verticillium wilt of the olive tree

small olive tree on wall

Unfortunately, we don’t have good news for you. And there is no known cure for verticillium wilt in olive trees. Once a tree is infected, the disease spreads rapidly through the tree’s vascular system, leading to its death. Additionally, if there are other olive trees in the area, or other plants or crops susceptible to this fungus, they may also succumb.

However, certain treatments can help control the spread of the disease and reduce its impact on the crop. We will tell you some of them so that if at any time you see your face with this disease, you know what you can do:

  • Remove infected trees: If a tree is heavily infected, removal may be the best option to prevent the disease from spreading to other nearby trees. It is recommended to cut them flush (removing even the roots) and burn them as soon as possible.
  • Pruning: Regular pruning can help reduce the disease burden on an infected tree, allowing it to concentrate on the healthiest branches and leaves. However, when the fungus attacks the roots, sometimes it does not help to save it.
  • Chemical treatments: Chemical treatments, such as fungicides, can help control the spread of the disease and reduce its impact on the crop.

If in the end you have to remove the olive tree, you must take into account that the fungus can remain in the ground, so the ground must be treated before planting anything.

How to Prevent Verticillium

There is no doubt that verticillium wilt of the olive tree is a practically fatal disease. This is why prevention is the best strategy to prevent the disease from affecting olive trees and other crops.

And what can you do to prevent it? Well, we recommend the following:

  • Select Resistant Varieties: Not all of them, but some varieties of olives are more resistant to this fungus.
  • Treat the soil: The fungus that causes Verticillium wilt can stay in the soil for many years, so cleaning it up is important. This includes crop rotation, soil disinfection before planting, and weed control.
  • Adequate watering: Olive trees need to be watered adequately to avoid water stress, which can make them more susceptible to Verticillium wilt infection. In this sense, avoid over-watering and do not do it during the hottest hours either.
  • Fight against insects and diseases: This way they will be less susceptible to fungi (because insects and other diseases can weaken them.
  • Proper pruning: Helps maintain the overall health of olive trees. You should remove dead and diseased wood, as well as avoid pruning during the wetter months.

Have you ever been confronted with verticillium wilt of the olive tree? What did you do to try to save the tree or those around it?

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