The robust and easy-care olive is not easily impressed by care mistakes. She stoically tolerates many rather suboptimal conditions and still thrives. Only two things can actually harm an olive tree: frost and a fungal disease.
Eye spot disease is common
The eye spot 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 shed from the tree.
Signs of eyespot disease
- Leaf is mostly affected at the end / the tip of the leaf
- Spots are small at first, but eventually grow larger
- affected leaves fall off
- branches can also die off
- Spots are round, light inside and darker outside
This fungal disease develops insidiously over several years and usually becomes apparent in spring or early summer. One treatment for this highly infectious disease - always remove and discard infected leaves immediately! - is usually only possible with chemical fungicides. Copper-based fungicides work 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 contained lactic acid bacteria fight the fungus in a natural way.
Other leaf spot disease
In addition to eyespot, another fungus causes leaf spots. Mycocentrospora cladosporioides is characterized by a yellowish coloration of the leaves, which are also speckled with black spots. Again, this fungus is best treated with a copper-based fungicide.
Fungal diseases often occur after lice infestation
The fungus Fumago vagans mainly covers the trunk 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 overwinters in warm rooms with high humidity. This fungus has little effect on the health of the affected olive tree, only affected leaves should be washed with soapy water.
tips and tricks
You can prevent many fungal diseases by overwintering the olive tree properly. Fungi appear more often when it is warm and the humidity is high. So it makes sense to spend the winter in a cool place, preferably outdoors.