Hello, We have a big 40' White Pine Tree in our front yard. About 1 month...

Asked July 20, 2015, 11:34 AM EDT

Hello, We have a big 40' White Pine Tree in our front yard. About 1 month ago, the top 1/3 of the tree trunk snapped and fell off. Looking at the fallen trunk it looked rotten. Yesterday my husband was under the tree and it dripped a lot of sap on him. He looked it up and said it could be Blister Rust. Do you suggest we cut off the 2 branches that have rust spots, or have the whole tree cut down? By the way, we have a lot of hollyhock and a lot of the leaves are yellowed. We read that this could be correlated?? Thank you for your expert opinion and thoughts. Sincerely, Beth and Steve Horner

Hennepin County Minnesota tree health white pine

1 Response

Thank you for the question. It is difficult to determine what is ailing your white pine. White pine blister rust is a fungal disease caused by Cronartium ribicola and it affects eastern white pine and currants or gooseberries, not hollyhocks. There is a complicated relationship between the white pine and the currants or gooseberries that host the fungus. Your hollyhocks may have hollyhock rust, an infection caused by the fungus Puccinia malvacearum. Here is a University of Minnesota publication on hollyhock rust: http://www.extension.umn.edu/garden/yard-garden/flowers/hollyhock-rust/

You need to have an accurate diagnosis of your tree's problem before you treat it. The University of Minnesota Extension website that has an excellent self diagnostic tool for you to use to evaluate causes other than white pine blister rust. Access the tool here: http://www.extension.umn.edu/garden/diagnose/plant/ .

If you decide that blister rust is the culprit, the only cure is to prune out infected branches because once the infection reaches the trunk, it will eventually kill the tree. Since your tree trunk has already snapped off, the disease may have already progressed IF blister rust is the cause. Here is another link specifically on white pine blister rust: http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/white-pine-blister-rust/

Thank you for contacting Extension.