Tiny Borer Beetles in Kwanzan Cherry Tree - Ask Extension
We have noticed limbs decaying on our Cherry tree and saw that there are very small beetles boring holes in the wood. We have removed the affected lim...
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Tiny Borer Beetles in Kwanzan Cherry Tree #879297
Asked July 29, 2024, 4:29 PM EDT
We have noticed limbs decaying on our Cherry tree and saw that there are very small beetles boring holes in the wood. We have removed the affected limbs and would like to know what kind of treatment we can use to preserve the tree? We've noticed several other trees on our street with the same issue. Thanks for your help!
Montgomery County Maryland
Expert Response
This may be a type of bark beetle (refer to the linked page for information and a comparison to the similar-looking Ambrosia beetle group). Beetles that bore into tree trunks and branches tend to target trees that are already stressed, even if clear indications of that stress (wilting foliage, for example) are not yet obvious. Some borers take advantage of drought stress, while others take advantage of over-watering and root loss. Cherries are not super drought-tolerant, but they are also quite sensitive to being over-watered or having root oxygen depravation by other means (like heavy soil compaction from regular foot traffic over the root zone).
The prevention of bark and Ambrosia beetle invasion focuses on maintaining tree health and vigor, so they are not stressed enough to become appealing to the beetles (and more vulnerable to their damage) in the first place. No treatment can eradicate any borers already in the wood, and while certain preventative treatments might discourage them from entering a new tree or re-infesting a tree already damaged, it's not an option we usually recommend. This is because the insecticides involved (often in the chemical group called pyrethroids), applied as a bark spray on the trunk or main branches, are ingredients that are non-selective; they can potentially kill any insect that comes into contact with spray residues, beneficial or otherwise. They also need to be applied with the right timing (to kill adult beetles landing on the bark ready to lay eggs for a new generation), and that timing can depend on the identification of the beetle, as life cycles differ and some require microscope examination to ID to species level.
For now, we would just recommend that you monitor the tree for watering needs as this drought continues. If a mature tree is declining, you could also have it evaluated by a certified arborist or licensed tree expert to see if they can diagnose the issue, as well as look for sources of tree stress (girdling roots, perhaps) that might be able to be alleviated.
Miri
The prevention of bark and Ambrosia beetle invasion focuses on maintaining tree health and vigor, so they are not stressed enough to become appealing to the beetles (and more vulnerable to their damage) in the first place. No treatment can eradicate any borers already in the wood, and while certain preventative treatments might discourage them from entering a new tree or re-infesting a tree already damaged, it's not an option we usually recommend. This is because the insecticides involved (often in the chemical group called pyrethroids), applied as a bark spray on the trunk or main branches, are ingredients that are non-selective; they can potentially kill any insect that comes into contact with spray residues, beneficial or otherwise. They also need to be applied with the right timing (to kill adult beetles landing on the bark ready to lay eggs for a new generation), and that timing can depend on the identification of the beetle, as life cycles differ and some require microscope examination to ID to species level.
For now, we would just recommend that you monitor the tree for watering needs as this drought continues. If a mature tree is declining, you could also have it evaluated by a certified arborist or licensed tree expert to see if they can diagnose the issue, as well as look for sources of tree stress (girdling roots, perhaps) that might be able to be alleviated.
Miri
