Yellow leaf on the olive tree: diseases causing this symptom

The olive tree with yellow leaves is sick

The olive tree is a fruit tree that generally does not have serious problems: it can be attacked by a cochineal, or it can be very thirsty following a drought that lasts too long, but it is really not a tree that requires a lot of care. However, in the event that its health weakens, one of the first symptoms that we will see is the yellowing of the leaves.

Being quite fragile and vulnerable, the foliage of a plant is usually the first part of its body to change: it changes color, loses its firmness and, in some cases, even bends. That’s why we want you to know what are the diseases of the olive tree whose main symptom is the yellowing of the leaves so that you can take the necessary measures so that new damage does not appear.



Prays oleae is a pest that causes yellow spots

Image – Wikimedia/Giancarlo Dessi

Although it is not a plant usually affected by pests, on some occasions it can be seen that it has them. These are insects that they are very active in summer and rest or hibernate in winter. I say “generally” because one winter may be particularly warm, and of course that stimulates some.

Pests that cause yellowing of olive leaves are:

  • Driller: precisely, the Phoeotribus scarabaeoides. It is a beetle which, in its larval phase, feeds on the interior of the branches and the trunk of the tree. This causes the olive tree to weaken and its leaves to turn yellow until they eventually fall off. Unfortunately, there is no curative treatment, but there is a preventive one: pruning remains must be eliminated, as well as brittle branches.
  • olive moth (Pray oleae): it is an insect that goes through three phases of development: the phyllophage, that is to say when it feeds on the leaves and tender stems; the antófaga, that is to say when it feeds on the flowers; and finally the carpófaga, which is when it destroys the fruit. To avoid this, treatments with specific insecticides must be carried out. More information.


Xylella is a bacterial disease

Image – Wikimedia/Sjor

As far as diseases are concerned, these can be caused by fungi, viruses or bacteria. Many pathogenic species use an insect as a vector; that is to say that as soon as it bites a leaf, a flower or a fruit, the micro-organism penetrates inside the plant through the mouth apparatus of the animal. Therefore, it will not be enough in all cases to treat the disease itself, but the insect that transmits it will also need to be controlled.

But which ones cause the leaves to turn yellow?

  • I repeat: it is a disease transmitted by the fungus Spilocaea oleagina which causes the appearance of spots on the leaves, first yellow and then brown. It is one of the most harmful, as it considerably weakens the tree, and therefore reduces its production. It needs to be treated with fungicides like this, but it’s best to take good care of the plant, and even make sure the variety you want to buy is repilo resistant.
  • Xylella fastidiosa: it is a relatively new disease in Spain, since it was detected in 2016. It is caused by a bacterium (X. fastidiosa) native to northern California (USA). Its vectors are those insects that feed on the wood of plants. And the symptoms it produces are progressive yellowing of the leaves and weakening of the tree. Unfortunately, there is no cure, but if the olive tree is not thirsty, and if it is paid regularly, the risk of being affected by this bacterium can be reduced. More information.

Other problems

The olive tree is a resistant tree

Image – Wikimedia/Burkhard Mücke

Although, as we have seen, there are pests and diseases that cause yellowing of olive leaves, the cause can sometimes be, for example, an excess or lack of water, or even in the soil. Let’s talk about it:

Excess or lack of water

Our protagonist is an evergreen fruit tree native to the Mediterranean. In this region, the summers are very hot (they can reach 41-42 ºC in some places and have several nights with lows above 20 ºC) and the winters are mild (except in the highest peaks, where there can be frosts down to -12°C, it is normal for it not to drop below 7°C. Indeed, at low altitude it is rare for it to drop below -2°C). Yes If we talk about the rains, they are very rare: between 250 and 700 mm of precipitation per year on average, although they can exceed 1000 mm.

The olive tree is therefore able to live with little water. In addition, in Mallorca, where I live, they are grown without any problems in areas where they do not exceed 300 mm of annual rainfall. And I can assure you that the harvest is good. Therefore, it is very important to take this into account, because it does not need as much water as other fruit trees.

It’s more, if it is planted in the ground, it will be enough to water it if it is seen that the drought has lasted several weeks and that it is very hot. Of course, we will also have to do this if it is in a pot, since it is normal for the soil to dry out very quickly.

What are the symptoms of too much or too little water in the olive tree? The yellow leaves. In the first case we will see that the first to change color will be the oldest, and in the second the youngest. To recover our tree we will have to suspend irrigation if we find that we are watering too much and also treat it with a fungicide so that the mushrooms do not harm him; and on the contrary it will have to be watered more often if it dries out.

Usually I

Although it is a fruit tree that grows in poor soils, don’t make the mistake of planting it in one that is very heavy and compact. And that’s it, he can tolerate a one-time flood, but if his roots are always flooded, they will soon die. For this reason, before planting it in the orchard or garden, you must see if it has good drainage, because if the soil does not absorb water quickly, then it will not be good for the olive tree.

But this has a fairly simple solution: it is simply a matter of digging a large hole, 1 x 1 meter, and filling it with a mixture of black peat and perlite in equal parts.

As you have seen, the olive tree can have yellow leaves for different reasons.

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