aspen disease - Ask Extension
I Have four clusters of young aspens that were planted in our yard before we bought the house. They are roughly 10 years old. Two stems have oozing bl...
Knowledgebase
aspen disease #775715
Asked October 18, 2021, 2:26 PM EDT
I Have four clusters of young aspens that were planted in our yard before we bought the house. They are roughly 10 years old. Two stems have oozing black stuff coming out of places where the trunk was scraped. Some of the exudate almost looks like sawdust when dry. No obvious foliar damage. Wasps seem to love the exudate.
Larimer County Colorado
Expert Response
Hi Robin,
This is just sap that has found its way outside through cracks in the trunk. It's sweet (because it's mostly sugar) which is why yellowjackets and wasps like it. There's nothing you can do to prevent it, except prevent further stress to the trees.
Aspen struggle in the urban landscape and like it at higher elevations. Water the trees as you're able. If you can replace the rock mulch with wood mulch, that's a good effort. Avoid unnecessary pruning and when you do prune, make proper pruning cuts.