Verticillium wilt is common on trees, shrubs, vegetables and fruits. Discoloration of the vascular tissue sometimes can be seen when you cut diagonally through a branch. There are no effective chemical controls for wilts. Growing resistant species, maintaining plant vigor and sanitation provide the only controls. Smut fungi produce large amounts of black sooty spores which show up as unsightly dark brown or black blotches on leaves, stems and fruit.
Corn smut is the common example in Ohio.
Resistant cultivars and protective sprays provide control. They produce chemicals that destroy plant tissue or cause abnormal growth. Bacteria enter through wounds, stomata or other natural openings. Bacteria can cause leaf spotting as on English ivy. Fireblight on crabapples, pears, mountain ash, hawthorn, cotoneaster and pyracantha is a bacterial disease.