A very serious illness is coming from the fungus Verticillium dahliae Kleb. Some of the branches dry out, but seldom the whole tree.
In the newer trees the first symptoms appear in the spring, on the top of the one year old branches. The leaves turn black, dry out and fall. The flowers and the fruits also fall. This illness shows more in the summer and fall, mainly in the irrigated olive orchards.
The attacked olive trees are spotted easily, because of their dried branches. In the nursery, they fade all of a sudden. On the older trees, the olive oil production gets reduced and the leaves fall. This fungus stays in the ground and is contagious through irrigation.
We should avoid cultivating olive trees, together with cotton, eggplant, tomatoes and other vegetables, which are sensitive to the fungus.
There are no cures for it. The only way it should be treated, is by cutting the dried parts and burning the trees. Disinfection of the ground should follow. The pruning tools should be disinfected after their use. Using enduring varieties and grafting are good ways to face and minimize this illness.
The soot is a fungus, coming from the Fumago vagans and the Antenaria elaeophila. These funguses cover the leaves with black plaster, they don’t parasite on the masts of the olive tree and they grow on the secretions of the insects, preventing the natural function of the tree. The best way to face them, is fighting against the insects. The best results from the fight against this fungus, are the combination of fungus and insect killers.
The fungus Gloeosportum olivarum Alm, damages olive orchards in the moisture territories and especially the coastal ones. The fungus attacks the olive fruit, young branches and leaves. The olives get attacked when they are ripening and they rotten. The olives that are wounded from hail are very susceptible to this fungus, when there is high atmospheric moist.
The green olives have more endurance to the fungus. The olive oil that is produced from olives that have been attacked from the fungus, is not superior quality, and certainly not extra virgin olive oil. The attacked leaves and young branches dry out and die. The attack is taking place in the fall and beginning of winter when the temperature and moisture of the atmosphere are favorable.
The extermination of the fungus is done by spraying with Liquid Copper Fungicide Spray.
The fungus Polyporus spp., Polystictus spp., Poria spp., Stereum spp., and Irpex spp., attacks the trunk and branches. This is a very spreaded disease, that attacks older trees, with results the rotting of the trees. The pathogenics of the fungus, get into the trees from the wounds of the pruning, and develop easier, where the rain water sits.