Beetles Boring Holes In Trunk Of Japanese Maple

Filed Under: Trees, Insects · Keywords: Japanese Maple, Holes, Trunk, Bark, Beetle · 5309 Views
Concerned my Dad's favorite Japanese Maple has ambrosia beetle.
Maple is about 30 years old. Was bought with house and previous owner said it was 15 years at the time and 15 more years have passed. It has always been gorgeous with no issues.

The bark was widening at areas a few years back, I thought perhaps drought and freezing winters, and didn't seem to bother it. This year I am seeing sawdust at foot of tree, tiny hole and what might be toothpicks. it seems to have been dropping leaves and turned it's magical orange/red flamed leaves leaves entirely too early. The leaves usually turn around early October.

I had privets this past spring that I posted that Mr. Heder correctly diagnosed with Ambrosia beetle. I posted a follow up picture that they are coming back but I am sure a maple does not come back, does it?
Let me know you thoughts. Kind regards, ~ Jeannine

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Answer #1 · Maple Tree's Answer · Hi Jeannine-The pictures are great but they make me extremely sad to see what they are showing. As a collector of Japanese maples it is always heartbreaking to think of losing an older beautiful tree.

The sawdust (frass) and toothpick looking structures definitely indicate the Asian ambrosia beetle has entered the tree. From what I know this pest has become a problem throughout the United States but seems to be most prevalent throughout the Southeast. Unfortunately this beetle is not easily controlled once it enters a shrub or tree. The only time it can be killed with any treatment is in the spring when the female beetle emerges from her winter home inside the infested tree and is moving to another area of the same tree or another tree or shrub to bore into. The beetles don't actually eat the trees wood but bore into the tree making tunnels that serve as habitat. The beetle introduces a fungus into the tunnels that the beetles larvae feed on. Not the tunneling of this beetle but this fungus is what will eventually kill the tree by clogging the vascular system. The Japanese maple along with several other trees with thinner barks seem to be more susceptible to this infestation. Systemic insecticides are usually not very effective either once the beetle has entered the inner wood of the tree.

The changing of leaf coloring and thinning foliage early is a sign the tree is definitely being stressed. I don't believe the cracking or splitting of the bark is due to only this beetles infestation. Possibly older wounds from breaking limbs, pruned limbs, mechanical damage, or cold temperatures with winter direct sunlight quickly thawing the bark may have caused the bark splitting at times during the trees life. Damage to the bark could have definitely attributed to the easier entry of this boring insect. Many boring insects will take advantage of shrubs and trees that are not healthy or have wounds allowing easier entry into wood beyond the bark.

If the tree was younger and healthy with only a few areas shown to be affected some cutting out of a few infected limbs and the spraying of a trunk insecticide may save the tree. Because of the age of the tree and the amount of infestation, especially the lower trunk, I don't believe the tree can be saved. From the looks of the tree now it most likely will die. If you decide to remove the tree make sure you dispose of it and don't add any part of it to a compost pile. The fungus could possibly infect other plants.

I remember the problem you had on your privet hedge plants with this beetle. I was wondering if you live close to your fathers home. It may be possible the same beetles had traveled to this tree as a new habitat to establish themselves in. I was glad to see your privet is recovering nicely after being cut back some months ago. It really looks great and healthy.

Wish I had some better news regarding a way to save this tree. Please ask if you have any other questions.


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Blumschen · Gardenality Seedling · Zone 7B · 5° to 10° F
Gratitude for your reply.
I just knew after my experience that this was a high possibility.
My folks live 8 miles south of me. 7B as well.

This tree is the King or Queen of the back yard, right outside their living room and screened porch.
They will be really sad. The bark is most definitely weather related.

This will be a huge setback for them again, as a new neighbor moved in next to them and took out a 50-75 year old Elm and anything else that was living in the yard, that backed up to my parents house and the other side of the garden. The Elm was majestic. Very upsetting.

I'll tell the Colonel the sad news today.

My husband had a few questions:
1. When you have had an infestation, is there advise about pruning in the garden going forward? Is there a better time of year?
I need to prune some bushes and limb up some trees this Fall or Winter.
2. Once the beetle emerges, what is it eating? the young eat the fungus but what is it that the adult eats?

I think this would be a great forum discussion to start!

Thanks for your time. ~ Jeannine

7 years ago ·
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Blumschen · Gardenality Seedling · Zone 7B · 5° to 10° F
Should I be using something like Bayer Advanced Tree & Shrub around the garden before pruning/limbing up takes place?
I dislike using these products, as I have a large songbird population here, but the possibility of the beetle still being around is very high, I suppose?
I have Sassafras, Oaks and some Leyland's that I need to limb up.
I'm even worried about doing selective pruning of my own Japanese Maples too.

The hard prune of the Privets made it venerable, I am guessing.

7 years ago ·
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Maple Tree

Maple Tree · Gardenality Genius · Zone 10A · 30° to 35° F
Don't be afraid to prune in order to keep your garden healthy. If the beetles are around keeping a close eye on your trees and shrubs for any signs of holes from borers is about all you can do. Possible preventative spraying in the early spring or catching an borers early will help to stop any further infestation.

7 years ago ·
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Maple Tree

Maple Tree · Gardenality Genius · Zone 10A · 30° to 35° F
From what I know the adults also eat the fungus and types of bacteria they cultivate in their tunnels. There is very little know about this specific fungi but it seems it solely relies on this beetle for its transport and proper environment for its growth.
As far as pruning I noted a few links below that will tell you how and when to prune trees and shrubs. There are many articles in gardenality on pruning specific types of plants. You can click on the articles tab above and type in a key word such as 'Prune' to find many articles that will help. Once you have had an infestation of this beetle getting rid of any infected trees and shrubs is about all you can do. Maintaining healthy trees and shrubs is the best defence against this pest as it will attack weak hosts before any others. Disposing of infected wood at this time of year should help to get rid of most of the beetles in the garden. I don't believe Bayer Advanced Tree & Shrub will kill this beetle as I don't think it contains a pyrethroid such as permethrin or bifenthrin which is recommended by several cooperative extension services. Many nurseries will carry landscape borer sprays containing a pyrthroid mentioned.

7 years ago ·
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Answer #2 · Blumschen's Answer · I finally found a write-up answering some questions that other Gardenality friends might be looking for:

In contrast to true bark beetles that live and
feed only in a narrow zone just under the bark
(Fig. 2,B) (hence, the common names “bark
beetles” or “inner bark borers”), ambrosia
beetles do not eat woody material and spend
no time beneath bark. They provide for their
own nutrition by feeding on a fungus that flourishes
within the galleries. These “fungus gardens”
originate from spores that female beetles
carry with them in special pocket-like structures
associated with their exoskeleton or
“skin.” The inoculum is passed from one beetle
generation to the next. Both larvae and adults
feed on this “ambrosia.” The fungus is responsible
for the black stain that accompanies each
tunnel. Some ambrosia beetles deposit eggs
directly in the tunnel, others excavate short
galleries, called “cradles” (Fig. 2), along the
sides of the main gallery. Fungal spores are
extruded into each cradle and (or) tunnel. By
the time eggs hatch there is plenty of mycelium
(my-seal-ium), a mat of thread-like tubes
that constitute the vegetative structure of the
fungus, to nourish both adults and developing

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