Larvae in Douglas Fir stump - Ask Extension
I found a 1/2" grub in a large Douglas fir stump. The stump is located at about the 900' elevation in the Coast range. Can you identify it, and...
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Larvae in Douglas Fir stump #838191
Asked June 29, 2023, 3:04 AM EDT
I found a 1/2" grub in a large Douglas fir stump. The stump is located at about the 900' elevation in the Coast range. Can you identify it, and is it harmful to the environment or wood structures?
Tillamook County Oregon
Expert Response
Hi Ellen,
I will forward this inquiry to someone who may be able to better answer this question as I am not 100% sure on the beetle species in the photos. These photos are very good, by the way! There may be someone who can potentially spot-ID this larval species and confirm for you.
Thank you for contacting Ask Extension!
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Brittny J.
Hi Ellen,
That is a beetle larva called a round-headed borer (family: Cerambycidae). The adults are called longhorn beetles, referring to their long antennae.
These beetle larvae typically live in and feed on the wood of diseased, damaged, dying or recently dead trees and shrubs. As such, they help recycle dead wood in forests. They can sometimes also colonize recently felled trees though, so they are not universally popular with folks in the timber industry. The adults can emerge from wood in structures or wooden objects if the lumber used is not properly kiln dried. The damage in structures is usually cosmetic, though, and these beetles do not re-infest lumber in buildings, so infestations do not perpetuate themselves.
The book Western Forest Insects lists 10 species of round-headed borers that are known to use damaged, dying or recently dead Douglas-firs as host trees, but I can't tell which species that is from looking at the larva. Adults are easier to identify to species.
These species listed in Western Forest Insects are all native and are part of the natural biodiversity in our region.
Hope that helps!
Yours,
That is a beetle larva called a round-headed borer (family: Cerambycidae). The adults are called longhorn beetles, referring to their long antennae.
These beetle larvae typically live in and feed on the wood of diseased, damaged, dying or recently dead trees and shrubs. As such, they help recycle dead wood in forests. They can sometimes also colonize recently felled trees though, so they are not universally popular with folks in the timber industry. The adults can emerge from wood in structures or wooden objects if the lumber used is not properly kiln dried. The damage in structures is usually cosmetic, though, and these beetles do not re-infest lumber in buildings, so infestations do not perpetuate themselves.
The book Western Forest Insects lists 10 species of round-headed borers that are known to use damaged, dying or recently dead Douglas-firs as host trees, but I can't tell which species that is from looking at the larva. Adults are easier to identify to species.
These species listed in Western Forest Insects are all native and are part of the natural biodiversity in our region.
Hope that helps!
Yours,
