The robust and easy-care olive is not easily affected by care errors. She stoically accepts many rather suboptimal conditions and still thrives. Only two things can actually harm an olive tree: frost and a fungal disease.
What fungal infections occur on olive trees and how can they be treated?
Eyespot disease or Mycocentrospora cladosporioides is often involved in a fungal attack on the olive tree. Chemical fungicides based on copper or home remedies containing lactic acid such as whole milk and water are suitable for treating infected leaves and twigs.
Eye spot disease is common
The eyespot disease, also known as “peacock eye”, is one of the most common fungal diseases in plants in our latitudes - of course it also affects olives. This disease is manifested by necrotic spots on the leaves and is caused by the fungus Spilocaea oleagina. The affected leaves are usually thrown off the tree.
Characteristics of eyespot disease
- Leaf is usually affected at the end/tip of the leaf
- Spots start out small, eventually get bigger
- affected leaves fall off
- branches can also die
- Spots are round, light on the inside and darker on the outside
This fungal disease develops gradually over several years and usually becomes apparent in spring or early summer. Treatment for this highly infectious disease – always remove and dispose of affected leaves immediately! – is usually only possible with chemical fungicides. Copper-based fungicides are best. If the infestation is only minor, you can also add one part whole milk to nine parts water and apply this mixture to the leaves using a spray bottle. The lactic acid bacteria contained fight the fungus naturally.
Other leaf spot disease
In addition to eyespot, another fungus causes leaf spots. Mycocentrospora cladosporioides has a yellowish color to the leaves and they are also speckled with black spots. This fungus is also best treated with a copper-containing fungicide.
Fungal diseases often occur after lice infestation
The fungus Fumago vagans covers the trunk in particular with a kind of dark soot. This sooty disease usually occurs as a result of an infestation with scale insects or mealybugs, but also when the olive is overwintered in warm rooms with high humidity. This fungus has little effect on the he alth of the infected olive tree; only affected leaves should be washed off with soapy water.
Tips & Tricks
You can prevent many fungal diseases by overwintering the olive tree correctly. Fungi appear more often when it is warm and the humidity is high. That's why it makes sense to spend the winter in a cool place, preferably outdoors.