Disease on the Stems of Azaleas

Botryosphaeria Canker

• Botryosphaeria cankers consist of several fungi such as fusicoccum, sphaeropsis, botryodiplodia and dothiorella. Typically, this disease is more likely to infect azalea plants that are already stressed or unhealthy. The fungal spores that cause this disease are spread by rain splash, contaminated pruning tools and insects. Gardeners see symptoms of botryosphaeria near areas where stems are wounded.

Symptoms

• Symptoms of botryosphaeria cankers include stem discoloration, sunken areas or swelling. Once a stem has been infected with the fungal disease, it begins to girdle, or prevent nutrients from moving to the rest of the stem. Gardeners may see leaves turn brown, die or defoliate from stem girdling. Also, botryosphaeria fungal spores produce small fruiting bodies that emerge through the canker or infected bark area. You must use cultural management options because there are no fungicides registered for controlling botryosphaeria cankers, according to the University of Georgia.

Pruning

• Sterilize your bypass shears to prevent spreading the disease to the rest of your azalea plant. Dip your bypass shears into a mixture of 70 percent denatured alcohol and 30 percent water. Wipe off the blades. Make sure you sterilize your pruning tool between cuts. Make a downward, 45 degree angled cut into 3 to 4 inches of healthy stem to remove diseased wood. Cutting at an angle prevents water accumulation on the wound, which reduces the risk of fungal diseases developing.

Prevention

• Maintaining a healthy azalea plant reduces instances of botryosphaeria cankers. Water-stressed azalea plants are the most likely to contract the disease. Monitor the weather and water your azalea plants during the summer or when the weather is hot. Apply water at the base of the plant in the morning to encourage evaporation off of leaves. Watering overhead can increase the risk of another fungal disease infecting your plant.