Dying Ponderosa Pine Trees in the foothills - Ask Extension
We live in Red Feather Lakes, Colorado and are seeing several of our Ponderosa Pine trees suddenly dying, some from the bottom up and some from the to...
Knowledgebase
Dying Ponderosa Pine Trees in the foothills #913864
Asked August 13, 2025, 11:13 AM EDT
We live in Red Feather Lakes, Colorado and are seeing several of our Ponderosa Pine trees suddenly dying, some from the bottom up and some from the top down. We have read on a local forum that it might be 'Pine Wilt' and that there is an injection available for correcting the situation. Could someone please give me information regarding this and what is recommended by your group for dealing with the problem, we are just sick to see our beloved trees failing, some of them are 18" to 20" in diameter and are well over a hundred years old. Thank you for your help with this.
Larimer County Colorado
Expert Response
Hi Audie,
Thanks for your question. Yes, we are seeing some pine wilt nematode throughout Colorado - both in more rural and urban areas. While it tends to affect non-native pine species (such as Austrian and Scots pine), it has been confirmed in natives, like ponderosa. This disease tends to start at the top of the tree and work its way down and the tree turns brown very quickly, usually in a matter of a few weeks. So it's possible that you're seeing this. If the tree is dying from the bottom up, it might be related more to drought or other environmental factors.
Trees can only be confirmed for PWN through molecular testing through a diagnostic lab. If you are interested in sending samples to the CSU Plant Diagnostic Lab, you can contact the lab for the best way to provide them with tissue. Generally it needs to be a "cookie" from the tree, freshly cut or from drill shavings: https://agsci.colostate.edu/agbio/plantclinic/
While there are treatments available for PWN, they are expensive, and are usually done for high-value trees, and trees that are NOT symptomatic (there is no cure once infection takes place). In addition, it's best if the trees can be watered prior to and after application.
The fact sheet on PWN has been recently updated and provides more details: https://extension.colostate.edu/resource/pine-wilt-disease/
Thanks for your question. Yes, we are seeing some pine wilt nematode throughout Colorado - both in more rural and urban areas. While it tends to affect non-native pine species (such as Austrian and Scots pine), it has been confirmed in natives, like ponderosa. This disease tends to start at the top of the tree and work its way down and the tree turns brown very quickly, usually in a matter of a few weeks. So it's possible that you're seeing this. If the tree is dying from the bottom up, it might be related more to drought or other environmental factors.
Trees can only be confirmed for PWN through molecular testing through a diagnostic lab. If you are interested in sending samples to the CSU Plant Diagnostic Lab, you can contact the lab for the best way to provide them with tissue. Generally it needs to be a "cookie" from the tree, freshly cut or from drill shavings: https://agsci.colostate.edu/agbio/plantclinic/
While there are treatments available for PWN, they are expensive, and are usually done for high-value trees, and trees that are NOT symptomatic (there is no cure once infection takes place). In addition, it's best if the trees can be watered prior to and after application.
The fact sheet on PWN has been recently updated and provides more details: https://extension.colostate.edu/resource/pine-wilt-disease/
