Telia erupting from infected cedar tissue immediately following a warm rain.
Photograph courtesy Mike BoehmDept Plant Pathology, The Ohio State University, 201 Kottman Hall2021 Coffey Road, Columbus, OH 43210-1087
Host (Latin and common name): Eastern Red Cedar (Juniperus virginiana) Quince (Cydonia oblonga)Disease name: Cedar-Quince RustPathogen name: Gymnosporangium clavipes
Rusts are caused by fungi in a group known as the Basidiomycetes. The basidiomycetes include a wide variety of fungi ranging from the mushrooms in our salads to those growing on decaying tree stumps. The rust fungi were so named because of the profuse number of rust-colored spores typically produced on the surface of infected plant tissue. The Romans were among the first to describe rust diseases of cereal crops and even had a god whom they worshiped to minimize disease outbreaks. Rusts are quite common and can be observed on many different plant species ranging from wheat and turfgrass to apples and snapdragons. Rust fungi have complex life cycles with some species requiring two different plant host species to complete their life cycles. In the case of cedar-quince rust, the fungus spends part of its time on quince and part on red-cedar. Cedar quince rust is caused by the fungus Gymnosporangium clavipes. The fungus alternates between junipers and a wide range of rosaceous (rose family) hosts. The disease can be striking on cedar (such as that shown above) following spring rains which stimulate the cedar-quince rust fungus to produce massive amounts of fruiting structures called telia. In the case of cedar-quince rust, these fruiting structures and their spores are exuded from slightly swollen cedar twigs in a red or rust-colored gelatinous matrix or slime. The slimy appearance disappears as the humidity decreases. Although fungicides can be used to manage this disease, other strategies such as avoiding planting both hosts in close proximity to one another or the use of rust-resistant cultivars is generally suggested.
APS publication number: IW000013
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