Infection on oak leaves causes small necrotic or chlorotic areas. On the underside of the leaves, yellow to orange spores may be visible. All spores, which infect both pine and oak, are primarily windborne. High humidity during spore dissemination increases the incidence of infection. Chemical control is usually neither necessary nor practical.
Symptoms consist of yellow spots on the needles, which appear during the spring.
They are followed by whitish blisters and orange spores. Infection may be serious enough to cause defoliation. The fungus infects aster or goldenrod during the summer and is able to overwinter in these plants, before it is carried to the pine again in the spring. Chemical control is usually not necessary. This disease is caused by the fungus Cronartium ribicola .