Diseases of olive (
Verticillium wilt
Verticillium wilt is caused by the soil borne fungus Verticillium dahliae. Symptoms include wilt and death of one or several branches (photo 1) of infected trees. In severe cases the entire tree may die. In the low deserts of Arizona, symptoms develop in the early spring and are most severe in years with cooler temperatures in February through May.
The fungus infects the tree through the roots, grows into the xylem and causes blockage of the vascular system. Substances produced in the plant during infection also may cause vascular discoloration, but this symptom is not always present. This is not a root rot disease, so decay of the root tissues does not occur.
Resistant rootstock of olive is available in trees for landscapes. There is no effective treatment once plants are infected.
1 
March 31, 2009