Cedar Apple Rust Control
CEDAR APPLE RUST CONTROLCedar Apple Rust is a fungal disease that requires both red cedar and apple trees to complete its life cycle. However, this disease does not pass between apple trees. If left untreated, can cause both foliage and fruit loss/damage.
|HOST PLANTS: Red Cedar Trees and Apples/Crabapples.
SYMPTOMS: The most conspicuous symptoms on apple are bright orange, glistening lesions on the leaves. Lesions which are not inhibited chemically may form small tufts of spore-producing structures on the lower surface of the leaf by July or August. Cedar-apple rust appears on fruit first as bright orange, slightly raised lesions, but may take on a more brown and cracked appearance as the fruit enlarges. Usually some of the orange color remains at harvest as evidence of the early season infection. Sporulation of fruit lesions is less common than that of leaf lesions. Stem infection causes a slight swelling of the stem and may result in abscission of the young fruit. On the cedar tree, cedar-apple rust produces brown, globular galls ranging in size from 1/4 inch (6-7 mm) to nearly two inches (50 mm) in diameter. These are dimpled like a golf ball in the dormant season, but produce gelatinous, orange spore horns during spring rains.
FAVORED ENVIRONMENT: The fungus overwinters on galls on the cedar tree. Wetting of galls in the spring initiates expansion of the spore horns and production of basidiospores which are carried to the apple tree to infect leaves and fruit during extended wetting periods. Lesions begin to appear 10 to 14 days after infection. In late summer, spores produced on the lower surface of infected apple leaves reinfect foliage of nearby cedar trees. These infections develop into galls which produce spores in the spring following the next full growing season. A cedar-apple rust gall produces spores only one season.
CEDAR APPLE RUST CONTROL: Choose resistant cultivars when available. If cedar apple rust is a continuing problem, organic fungicides can be applied weekly starting with bud break on apples and crabapples. Fungicide applications are used to protect the tree from spores being released by the juniper host in mid-spring. This occurs only once a year, so additional applications after this springtime spread are not necessary. Rake up and dispose of fallen leaves and other debris from under apple trees. Remove galls from infected junipers. In some cases, juniper plants should be removed entirely.