Godwin: Leaf gall caused by variety of fungi

Are you finding many soft distorted leaves on your azaleas, Camellia sasanqua and/or rhododendrons?

These thickened, curled, fleshy leaves range in color from pale green to white. The recent moist, cool weather arrived in time to increase the infection by the leaf gall fungus.

This disease is more alarming than damaging. Developing young leaves and stems are infected by fungus spores shortly after flowering. The spores germinate and grow on the tender foliage in the presence of moisture.

Infection can continue as long as sensitive immature leaves are on the plant. As the disease progresses, the leaves are covered with a white, powdery mass of spores produced by the fungus. These active spores are easily carried by the wind to other plants. At the end of the disease cycle, leaves turn brown and drop off.

Several fungi are responsible for infection of different plants.

Leaf gall caused by the fungus Exobasidium vaccinii is very common and widespread in the early spring on azaleas and rhododendrons. Camellia leaf gall is caused by the fungi Exobasidium camelliae. Blueberries, leucothoe and Japanese andromeda are susceptible to the fungus Exobasidium vaccinii, which infects young leaves, blossoms and sometimes young twigs or shoots.

The recommended control is to remove the leaf galls as soon as they are spotted. Galls removed should be destroyed and not left near infected plants. Leaving the galls on the plant increases the source of disease spores for the next year. If galls are frequently a problem, plan to remove and replace mulch around the plant. Pruning to increase air movement and sun also can slow infection.

Leaf gall seldom causes enough damage to justify spraying a fungicide.

Fungicidal treatments provide limited control. Timing of fungicide applications must be precise. New leaves need protection before they unfurl, and reapplication of a selected product is needed. Fungicide application after galls are present will not affect the disease.

Get some exercise and save some money by simply hand removing the leaf galls.

Peg Godwin is horticulture agent, Lenoir County Cooperative Extension Center. Reach her at Peg_Godwin@ncsu.edu or (252) 527-2191.