Oleander knot—Pseudomonas savastanoi pv. nerii
Pseudomonas savastanoi pv. nerii causes galls or knots on oleander stems, bark, and leaves. Twigs and branches can die back, but the overall plant health is usually not seriously threatened. Gall bacteria reproduce in fissured or galled bark and are spread by contaminated water, implements, or hands. Healthy tissue is infected through fresh wounds during wet weather. Susceptible wounds include frost cracks and any leaf scars on branches.
Avoid overhead watering. Prune out and dispose of infected tissue during the dry season. To prevent spreading pathogens on infected tools, clean tools of debris after each use and thoroughly spray them with disinfectant or soak them in disinfectant for one or more minutes. Tools can be sterilized using a commercial disinfectant as directed on the product label. Homeowners on their private property can use household bleach or disinfectant cleaners diluted 1 part disinfectant to 10 parts water.
galls on Oleander stem and leaves