The shoot and fruit swellings and orange spores that appear on hawthorns in summer are due to a fungal disease called cedar-quince rust. By fall, only the dark brown, dead, swollen branch tips may remain as evidence of the disease. The causal fungus, Gymnosporangium clavipes, spends part of its life on cedars and junipers and part on hawthorns, apples, crabapples, and quince.
Select hawthorn varieties that are disease resistant. Remove and destroy infected twigs, fruit and leaves from the hawthorn. Removing nearby cedars or junipers, the alternate hosts of the fungus, will help control this disease. However, spores from the junipers or cedars can travel a distance of a quarter of a mile or more. Fungicides can be used in early spring to prevent cedar-quince rust disease. Contact your local Cooperative Extension office for fungicide recommendations.
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