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Leaf Gall

How can I treat a leaf gall on my plant?

Symptom(s):

Exobasidium vaccinii causes leaves and flowers to become swollen, curled, waxy and fleshy (Fig. 1). The swollen plant tissues or "galls" are made up of abnormal plant tissue. Infected leaf tissue is usually pale green in color during the early stages of the disease; infected flowers are usually pinkish. Later in the season, a white spore layer covers the infected plant parts. Galls eventually turn brown and harden as the season progresses. Lower leaves on plants are usually the most seriously damaged, but under humid conditions and in shaded locations galls may occur at the ends of upper branches.

Cause(s):

The occurrence and intensity of the disease depends on weather conditions and on the source of the causal fungus. Spores produced in the whitish mold on the surface of galls in late spring to early summer are blown and washed to leaf and flower buds where they cause new infections. Galls form the following spring. Cool, wet weather favors dispersal of the spores.

Control(s):

To control this problem, the galls should be handpicked and destroyed before they turn white. When only a few plants are involved, as in a home planting or a small greenhouse area, the disease is easily controlled by hand picking the galls and burning or burying them. To prevent new infections, it is important to pick the galls before the white spore layer appears. Fungicide control is generally not warranted in home landscapes.

Reference(s):