What are these grubs and bugs in bark?

Asked August 26, 2019, 8:44 PM EDT

What are these? I found them in the bark of the tree that was killed suddenly. Kiss one 80 year old noble fir goodbye (tree suddenly died). The sudden increase in sap holes in the neighboring noble fir (and none of the Douglas firs show signs) makes me believe that the ones that could move did. The top of the tree ~15 feet is now dead) We're treating the trees with an over the counter pesticide filled fertilizer. What else should we do?

Washington County Oregon forestry insect issues urban forestry

1 Response

That's a lot of creepy crawlies! Those larvae and pupa are of a longhorn beetle. There are a number of species of longhorn beetles in our area. They could be the Oregon fir sawyer, for example. The important thing to know as that these wood boring beetles are not the thing that kills trees. They go after recently killed trees, or ones that are in serious decline. I am not sure what the adult pictured is.

Unfortunately, we are seeing a lot of mature firs (noble firs, grand firs) that are dying in the region that seem to have succumbed to the effects of prolonged hot and dry years. Even though this summer has been mild, the cumulative effects of previous dry and hot years ultimately catch up with the tree.

There is no reason to treat your remaining trees with the pesticide/fertilizer product. Fertilizer, especially, is a bad idea when trees are under stress, because they increase the tree's demand for water, and can further stress the tree. If the insects are moving into a new tree, then that tree is already declining and killing the insects won't solve the problem.

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