Fungi can show signs in many different forms. Most commonly, you will notice fungus issues on the plant foliage. Black spots on leaves (lesions), holes in leaves (this is common to laurels and cherry trees when stricken with shot hole disease), and discoloration know as blight. Some uncommon signs of a fungal problem would be substances forming on the branches. Possibly a powdery, green substance or in some cases a gall (which is the swelling of an infected area of the branch).