I live in Beaverton and I want to prune my two large ash trees before the fall winds come. I think emerald ash borers would find the sap from my pruned trees attractive. When is it safe to prune my ash trees?
The best time to prune trees in general is late fall and early spring when potentially damaging insects are inactive and not flying around, and when the tree is dormant. For wood-boring beetles like emerald ash borer, that is usually around March and after September but can vary depending on temperatures.
It is also important that you do not move wood from your tree, especially as firewood into other places, especially in other counties. This is one of the main ways that this pest gets introduced to new areas. It is recommended that you cut your firewood into small pieces so it dries out quickly and even smaller pieces if it is to be left on site.
As a reminder, all ash trees are susceptible to attack from emerald ash borer, whether they are healthy or not. Regardless, it is highly recommended to do what you can to keep your tree(s) healthy. It sounds like you are doing just that.
For more information on emerald ash borer, check out the OSU Extension resource collection below.
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