Scots Pine Blister Rust

**This organism is not known to be present in the United States but poses a threat. Scots pine blister rust is an aggressive fungus that attacks a wide variety of hard pine species. It is native to Europe and Asia and is not known to be in the US, but poses a serious threat should it be introduced. Scots pine blister rust damages vascular tissue and kills the cambium of infested trees, leading to girdling and eventual death. It is more virulent than white pine blister rust, which has already cost over $1 billion dollars to manage in the US. This fungus decimated two-needle pine forests of the Mediterranean region in the 1960s and 70s, and infected or killed half of a 10,000 square kilometer pine forest in Greece over a six year period. Impacts should this fungus establish in the US are considered incalculable. Scots pine blister rust has a complicated life cycle that uses both pines and alternate, herbaceous hosts. The wide range of alternate host species include many common garden plants like peonies, impatiens, gentians and verbenas, wildflowers including paintbrush and milkweeds, and common weeds such as swallow-worts and speedwells.


Scots pine blister rust can be dormant for up to two years after infection, which makes detection in imported materials challenging. This disease has been frequently intercepted, particularly in arriving pines for bonsai and peonies from a variety of European and Asian countries. The risk of its establishment in the US under current trade regulations is high. Once established, the disease could be spread unknowingly on infected plant material and naturally by wind.


Think you've spotted this pest?

If you think you've found this pest in your landscape contact your local extension office to see about sending in a sample.
Find your local extension office here.