Disease or Plague in Holm Oaks. Diagnosis of a Real Case

Good farmers! The topic that we are going to deal with today is a practical case, it is treated as the title of disease or plague in oaks says. Agrohuerter Alberto de Almería (Spain), who contacted us some time ago about the problem his almond trees were having; he has written to us again, this time it is due to a disease or plague of the oaks. He tells us that a few weeks ago there were heavy rains in his area. In his orchard, which is in the open air, and in which he has various trees in large gardens, among them these oaks, they were strongly attacked by a fungus.

Therefore, what he did was an ecological treatment on them, first he used a milk-based fungicide and the next day he only treated with bicarbonate, and after this the plants worsened even more.

Next we are going to analyze the disease or plague in oaks.

White spots on the leaves of the oaks, what can it be?

At first they had white spots, just after the rains.

The leaves of the oaks, especially the terminal ones and the young shoots, are rolled up on themselves inwards. On the other hand, as observed on the edges of these, there is necrosis, that is, their appearance is as if they had been burned.

Although some leaves ended up drying and falling, the plants have not died. After having examined the leaves, neither insects nor eggs have been found, but silk strands, although very few and scattered.

How to combat holm oak fungi?

The fact that there are white areas and threads, it is most likely a fungus. As we mentioned at the beginning, what was done was to treat with milk fungicide and the next day treated with bicarbonate.

The fungi have been able to be controlled, but what a fungus does not usually produce is the appearance of a burned leaf. This is why the problem comes after having treated with these fungicides.

I have to clarify that fungicides should be applied on dry days, because otherwise they can cause problems or lose effectiveness.

Really 3 things could have happened:

1. That the plant has been burned by excess bicarbonate, which is a compound with a very high pH, ​​making it alkaline (basic pH). This may have happened because the bicarbonate has been poorly diluted, or because an excessive amount has been added. What happens in a soil or substrate with a very high pH is that certain nutrients disappear.

2. That with the rains, the substrate of the plant has been washed, that is, minerals and nutrients that it had were lost, so the plant no longer has them.

3. That it be a mixture of the two previous cases, that is to say that adding substances with a basic pH causes nutrients to be lost, to which is added more loss of these due to washing due to heavy rains. All this makes the lack of nutrients in the substrate visible in the plant.

Due to the symptoms, that the edges of the leaves begin to be affected first, it could be a lack of Potassium (K); but this can only be confirmed if an analysis is carried out.

General solutions to cure oaks

For fungi, the fungicide treatment has been carried out correctly; although as we always say it is better to prevent, because it is more difficult to combat it once the fungus is installed. These treatments are recommended to be sprayed on the leaves and on days when it does not rain, or when there is not much humidity in the environment. On the other hand, if you use bicarbonate you should take into account that the solution is not too concentrated.

For the lack of nutrients, it is necessary to pay, but in adequate amounts. The ideal thing is to make more subscribers, even if they are in small quantities, and to see the evolution of the plant. To fertilize our organic garden, you can buy organic fertilizer, use the compost that we make ourselves or use earthworm humus.

What has finally happened to the oaks?

Finally, the holm oaks and Kermes oaks that were affected have recovered very well and have begun to sprout again, what was done was to provide earthworm humus. Which makes us think that it really lacked some nutrient.

References

• Karioti, A., Bilia, A.R., Skaltsa, H. (2010). Quercus ilex L.: A rich source of polyacylated flavonoid glucosides. FoodChemistry,123(1), 131-142.
• Karioti, A., Bilia, A.R., Skaltsa, H., Messori, L. (2009). Proanthocyanidin glycosides from the leaves of Quercus ilex L. (Fagaceae), Tetrahedron Letters, 50(16), 1771-1776.
• STONE, J., POLISHOOK, J., WHITE, J. (2004). 12 – ENDOPHYTIC FUNGI, Editor(s): GREGORY M. MUELLER, GERALD F. BILLS, MERCEDES S. FOSTER, Biodiversity of Fungi, Academic Press, 241-270.

We are glad to know that Alberto’s plants have been saved and also in an ecological way. Agrohuerters. You can tell us in comments if this has ever happened to you, advice about it or doubts that arise. As a last recommendation, if it rains a lot we can place a plastic in our garden.

Until next time Agrohuerters!