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Scots Pine Blister Rust (Cronartium flaccidum)
Scots Pine Blister Rust (Cronartium flaccidum) is primarily a disease of Scots pine (Pinus sylvestris), but it can also infect other two-needle pine species. It can be distinguished from white pine blister rust (C. ribicola) by its inability to infect five-needle pines. The heteroecious rust has a number of alternate hosts including members of the genera Paeonia, Asclepias, Delphinium, Impatiens, Myrica, and Tropaeolum which are commonly grown in Ohio. It does not infect Ribes spp., the alternate host for C. ribicola. The disease is distributed throughout Europe and Asia but is not known to occur in North America. Ohio has extensive native and non-native pine species, including Scots pine, which would be impacted should this disease be introduced to the state. Survey for this disease will be difficult because detection is easiest when the fungus is fruiting. Otherwise it is not visually detectable. Nonetheless, this disease is suitable for early detection survey and evidence of the fungus will be visually surveyed on Scots pine and any alternate host genera that happen to be present in the nursery.