Pleasing Fungus Beetles in California

Subject: Oak Tree Beetle
Location: Foothills east of Sacramento, Ca
August 1, 2016 7:11 am
I live in Northern California in the Sierra foothills. We recently had a large, established oak tree die. I noticed a couple nodes at the base that I was able to break off. I found an infestation of black and orange beetles. Trying to figure what they are, if they killed the tree or if they just move in after the tree is dead/dying. And what to do to make sure they don’t spread to our other trees.
Signature: Thank you, Ian

Pleasing Fungus Beetles
Pleasing Fungus Beetles

Dear Ian,
These are Pleasing Fungus Beetles, probably
Megalodacne fasciata, and they are not responsible for the death of your oak tree, however, their presence is tied to the health of the tree.  According to BugGuide:  “larvae and adults feed on the fruiting bodies of fungi growing in decaying wood.”  So, as the tree began to die, it was invaded by the fungus and the fungus attracted the Pleasing Fungus Beetles.

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