Common shrub diseases in Georgia range from minor leaf spots to fatal root rots. Bacteria, fungi and viruses need the proper environmental conditions to infect a shrub. Some diseases affect a select few shrubs while other diseases affect almost all shrubs.
The proper cultural care helps reduce and control shrub diseases in Georgia. Each species of shrub should receive the optimum amount of sun and water, be planted the correct distance apart and be fertilized regularly.
Fungal Leaf Diseases
Fungal leaf spots vary from tiny spots to large splotches with tan or brown centers and dark brown, reddish or purplish margins. Fungal leaf spots usually do not cause significant damage to shrubs in Georgia.
Raised bumps on the undersides of shrub foliage and yellowish spots on the tops of the foliage are symptoms of leaf rust. It is a fungal disease, and the bumps release powdery spores that are orange to rust colored.
Bacterial Leaf Diseases
Leaf galls are caused by the bacteria exobasidium. They are masses of off-color swollen leaf tissue which turn black and hard. The galls also attack the flowers and are common on azaleas, rhododendrons and camellias in Georgia. Although they are unsightly, the galls do not harm affected plants.
The bacterium Erwinia anylovora causes fire blight on plants in the Rosacea family, such as roses, crabapples, pears, cotoneasters and pyracanthas. Infected leaves and stems turn dry and crispy and appear burnt. Some stems bend back on themselves, forming a "shepherd's hook."
Fungal Root Rots
Soil-borne fungi, such as Pythium, Phytophthora, Rhizoctonia, and others, cause root rots on Georgia shrubs. Symptoms include poor or stunted growth, off-color foliage, yellowing and dropping of lower leaves, wilting or collapsing of affected shrubs, and even death. Root rots are the most harmful diseases of Georgia shrubs.
Bacterial diseases cause leaf spots and stem spots on shrubs in Georgia. The areas appear water-soaked or greasy and can lead to the decline and death of the affected plant.
The symptoms of viral diseases are cholorotic mottling, ringspots and stunted growth. There is no treatment for viral diseases and the plants must be destroyed.