User question:My oleander is sick all the time. It has blackish tumors on the twigs and leaves. The leaves fall and the branches dry up. I have a black oleander!
It is a bacteriosis (disease caused by bacteria) that is on your oleander. Not much to do when the disease is installed, very often brought by biting insects such as aphids. Cut the branches 10 cm below the affected parts. Sometimes a clear cut is necessary (flush cut). But once in two, the disease returns. It grows well in warm and humid atmospheres.
The oleander does not necessarily grow everywhere, it needs humidity but not stagnant. So a sunny location and draining soil with a supply of water in spring and a little in summer during flowering, but beware of excess.
Bordeaux mixture sprays are effective in prevention, as well as horsetail and nettle manure.
We notice that the addition of organic matter, compost, organic fertilizer... improves the structure of the soil and the plants are less sensitive to bacteriosis among others.
Warning:Compulsory disinfection pruning tools between each shrub.