Are box elder beetles harmful to fir trees? - Ask Extension
The last week or two we have noticed large swarms of what I think are box elder beetles on the trunks of 2 fir trees in our yard. When the afternoon ...
Knowledgebase
Are box elder beetles harmful to fir trees? #813789
Asked October 10, 2022, 1:09 PM EDT
The last week or two we have noticed large swarms of what I think are box elder beetles on the trunks of 2 fir trees in our yard. When the afternoon sun is on the trunks there are many hundreds if not thousands of them flying around near the trunk and crawling in and out of crevices and holes in the bark. In the morning when it is cool and shady, they are crammed into the holes where they spent the night. Are these definitely box elder beetles? From what I've read on-line, they are not supposed to be harmful, but I don't remember there being so many holes in the bark in the past.
Washington County Oregon
Expert Response
Thank you for the photos. These do appear to be adult box elder bugs (although the nymphs with red tend to be better known). Here is an Extension article which shows both in the first photo: http://ipm.ucanr.edu/PMG/PESTNOTES/pn74114.html
This article also has information about their potential harm to plants, and ways to keep them out of your home.
The holes in the bark are probably caused by some type of boring insect (as opposed to the bugs, which only suck out chlorophyll). We would need to know the exact species of fir, and have some information about the insect to tell you what species of borer your trees have. Are they Douglas fir (pseudotsuga) or true fir (Abies)? In the meantime, don't worry about the box elders. Good luck!
This article also has information about their potential harm to plants, and ways to keep them out of your home.
The holes in the bark are probably caused by some type of boring insect (as opposed to the bugs, which only suck out chlorophyll). We would need to know the exact species of fir, and have some information about the insect to tell you what species of borer your trees have. Are they Douglas fir (pseudotsuga) or true fir (Abies)? In the meantime, don't worry about the box elders. Good luck!
