Exobasidium vaccinii causes leaves and flowers to become swollen or thickened, curled, waxy and fleshy in appearance. This fungus causes leaves and flower petals to enlarge abnormally. It is commonly referred to as azalea leaf and flower gall.
Do you have azalea or camellia plants with leaves or flower petals that are swollen and malformed?
This unusual growth is caused by a fungus that can deform several different plants, including azalea, camellia, blueberry and fetterbush.
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Exobasidium vaccinii causes leaves and flowers to become swollen or thickened, curled, waxy and fleshy in appearance. This fungus causes leaves and flower petals to enlarge abnormally. It is commonly referred to as azalea leaf and flower gall.
Symptoms vary somewhat based on the host plant. Infected blueberry leaves turn an unusual bright red in spring with almost no swelling of tissue. With azaleas and camellias, leaves become large and distorted and eventually a white powder covers the galls.
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The white growth consists of spores, which is how the fungus reproduces. Galls ultimately turn brown and harden. Not every leaf will be infected. It’s more common for the plant’s lower leaves to be the most heavily infected. But under humid conditions and in shaded locations, galls may form on leaves throughout the plant canopy.
To reproduce, the disease relies on airborne spores produced in the whitish mold on the surface of galls in late spring to early summer. Some plant pathologists believe that once the spores are released, they are blown and washed to leaf and flower buds where they cause new infections.
Galls then form the following spring. Other plant pathologists think that the spores are produced the following year from old dried, brown galls that fell to the ground around infected plants the previous year. The spores then blow and splash onto new leaves and petals as they emerge in spring causing infection. One or both lines of thought may be true. But in either case, it’s important to remove and dispose of infected leaves before they turn white with spores.
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Once you see evidence of infected leaves, it’s too late for chemical control. Besides, there is no effective or practical fungicide to control this disease in the home landscape. But the amount of infection can be reduced by pruning and disposing of infected leaves before spores are produced. After removing infected leaves with galls, never leave them on the ground around the plants.
It’s best to bury, burn or place infected leaves in a bag and throw them away. This disease is more severe during a cool, wet spring. It’s advisable to not add to the problem by frequently using an overhead sprinkler and keeping the foliage wet in spring during disease development.
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In the home landscape, the fungus does not cause any long-term problems for plants. The infected leaves will usually fall prematurely.
Larry Williams is the Extension horticulture agent with the Okaloosa County Cooperative Extension Service, University of Florida. Contact Larry at 689-5850 or email [email protected]
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