| Cedar apple rust is caused by a fungus but unlike many diseases, this fungus requires two different trees (hosts) to complete its life cycle - a red cedar tree and an apple or hawthorn tree. The pathogen produces tumor-like growths (galls) on branches of red cedar trees but causes little damage to these trees. The disease also causes damage to apple or hawthorn leaves and fruit. Cedar apple rust is not uncommon in Florida but is not considered much of a threat. The disease causes great concern in states where apple orchards are big cash crops. |
 Mature cedar apple rust galls on a cedar tree Photo credit: Department of Plant Pathology, University of Missouri-Columbia |
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The life cycle starts in late summer when spores are produced on the leaves of hawthorn or apple trees. The spores are carried by wind to red cedar trees. The spores eventually develop into galls. The galls produce bright orange, jelly-like horns that create new spores. These new spores are carried by wind to apple and hawthorn trees where the cycle starts again. |
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Yellow spots that later turn brown are found on apple and hawthorn leaves. These spots cause the leaves to curl up and under. On red cedar trees, look for reddish-brown, round galls and, in the spring, the orange, jelly-like horns that develpop from the galls. |
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The primary hosts of cedar-apple rust are apple or hawthorn trees. The alternate hosts are red cedar trees. The disease is most commonly found in areas where apples or hawthorn trees are close to red cedar trees. |
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 Tendrils of cedar apple rust gall Photo: Minnesota Nat. Res. Dept. |
 Spots on apple leaves Photo: Minnesota Nat. Res. Dept. |
 Spots on hawthorn leaves Photo: Dep. of Plant Pathology, Univ. of Missouri-Columbia |
| [Forest Health] |
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