This morning I notied a couple of sap weeps on the trunk of
a seedling walnot tree planted about fifteen years ago. It
looks like something chewed holes in the trunk about two feet
above the ground, leaving a residue of cuttings in the entrance
hole and a bit of sap around it, with the excess dripping down.

Photos are in
http://www.zefox.net/~bp/walnut/

If anybody recognizes the pattern I'd be curious to know
what it is. The tree seems healthy, at least for now.

If anybody has a clue what it might be please let me know.

Thanks for reading,

bob prohaska

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On 7/10/2025 9:16 PM, [email protected] wrote:

This morning I notied a couple of sap weeps on the trunk of
a seedling walnot tree planted about fifteen years ago. It
looks like something chewed holes in the trunk about two feet
above the ground, leaving a residue of cuttings in the entrance
hole and a bit of sap around it, with the excess dripping down.

Photos are in
http://www.zefox.net/~bp/walnut/

If anybody recognizes the pattern I'd be curious to know
what it is. The tree seems healthy, at least for now.

If anybody has a clue what it might be please let me know.

Thanks for reading,

bob prohaska

Is it possible both are the result of vandalism? The second photo in particular shows something resembling a cut by a pruning saw.

I don't think the first photo is from an insect or a woodpecker. (On
the Zelkova tree in front of my house, a woodpecker made holes that
resembled the work of insect borers.) Also, it is too deep relative to
its diameter for it to be from a gnawing animal.

I would seal both holes with white glue (e.g.: Willhold, Elmer's, Glue
Bird). Do not use pruning paint, which can cause adjacent plant tissue
to die.

--
David E. Ross
Climate: California Mediterranean, see <http://www.rossde.com/garden/climate.html>

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[email protected] wrote in rec.gardens:

http://www.zefox.net/~bp/walnut/

Many different beetle grubs attack barks and cambium. Some do not
even threaten the tree seriously, but most do.

The holes look the same to me, no matter which species cause them. I
cannot find a beetle that would have a predilection for Nut Walnuts
other than a bork beetle “Pytyophthorus Juglandis”.

You will have to find the beetle, to know, I am afraid.

The risk with the Pytyophthorus Juglandis is that it transports a
fungus which destroys the tree. But there is nothing on your photos
that could identify the grub reliably.

Anyway. No chemical product exists which could act against an
ongoing infestation. Usually you have to get rid of the beetle.

At least, the grubs that destroy fruit trees, here in France, drills differently and you can even see the path that the animal takes
under the bark… oftentimes terminating in a second, bigger hole,
where the woodpecker intervened. We otherwise kill the beast by
pushing a small twig into the canal. The grub is usually at the end.
You see that you have killed it, when the twig is … humid at the
tip.

You could try that at the hole on your second picture. On the first,
the grub appears to have failed to enter the bark.

I am curious to read other opinions.

Cheerio
--
"I'd trade all my tomorrows for a single yesterday."
(Janis Joplin/Kris Kristofferson – Me And Bobby McGee)

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[email protected] wrote:

This morning I notied a couple of sap weeps on the trunk of
a seedling walnot tree planted about fifteen years ago. It
looks like something chewed holes in the trunk about two feet
above the ground, leaving a residue of cuttings in the entrance
hole and a bit of sap around it, with the excess dripping down.

Photos are in
http://www.zefox.net/~bp/walnut/

If anybody recognizes the pattern I'd be curious to know
what it is. The tree seems healthy, at least for now.

If anybody has a clue what it might be please let me know.

Thanks for reading,

bob prohaska

1st one looks like only mild damage to the bark without any
actual bore hole. the other it looks like there is debris or
frass from chewing indicating perhaps a bug ate inwards or
perhaps someone was shooting a bbgun and hit your tree.
exploring that hole might give some more information...

IMO trees are sturdy and can recover from damage of this
sort but if you do have an actual bug in there it would be
probably better to make sure it is dead and gone and then
the tree can heal over the wound.


songbird

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On 7/10/2025 10:48 PM, Michael Uplawski wrote:

[email protected] wrote in rec.gardens:

http://www.zefox.net/~bp/walnut/

[snipped]

Anyway. No chemical product exists which could act against an
ongoing infestation. Usually you have to get rid of the beetle.

[more snipped]

There are actually two chemical methods of eliminating borers in trees.

One involves a drench of Imidacloprid. The amount depends on the
diameter of the trunk at the height of your chest. The drench is
applied in the root zone. DO NOT use Imidacloprid while the tree or any adjacent plant is blooming because it is very harmful to bees. On the
other hand, it is harmless to birds and mammals; thus, nuts from the
tree would still be edible.

The other involves a small plastic capsule containing a systemic poison.
I don't remember the name of the poison or the brand name of the
capsule, but a comprehensive plant nursery would know of this. You
drill a spiral of 1-inch holes about 1-inch apart twice around the trunk
of the tree. The capsules should just fit snugly into the holes. You
then take a hammer and nail and gently puncture each capsule. This was
very effective in eliminating ash white-fly from my ash tree and should
also be effective against any kind of borer. However, I do not know if resulting fruits and nuts remain edible. Again, I would not use this
while the tree is in bloom because of bees.

--
David E. Ross
<http://www.rossde.com/

The stranger that sojourneth with you shall be
unto you as the home-born among you, and thou shalt
love him as thyself; for ye were strangers in the
land of Egypt: I am the LORD your God.
Leviticus 19:34

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David E. Ross <[email protected]d> wrote:

On 7/10/2025 10:48 PM, Michael Uplawski wrote:

[email protected] wrote in rec.gardens:

http://www.zefox.net/~bp/walnut/

[snipped]

Anyway. No chemical product exists which could act against an
ongoing infestation. Usually you have to get rid of the beetle.

[more snipped]

There are actually two chemical methods of eliminating borers in trees.

One involves a drench of Imidacloprid. The amount depends on the
diameter of the trunk at the height of your chest. The drench is
applied in the root zone. DO NOT use Imidacloprid while the tree or any adjacent plant is blooming because it is very harmful to bees. On the
other hand, it is harmless to birds and mammals; thus, nuts from the
tree would still be edible.

Last I heard imidocloprid has been banned in California as of this
year (or thereabouts), at least for retail sale.

The other involves a small plastic capsule containing a systemic poison.
I don't remember the name of the poison or the brand name of the

Perhaps AceCap? It's banned in California also. https://www.amleo.com/acecap-systemic-insecticide-tree-implants-50-pack/p/AC450 The capsules seem rather large, 3/8" (10 mm), so using them will do some appreciable damage. The holes looked small, less than 2 mm.

I tried probing the holes with a wire, it went in, seemingly straight,
about 9 or 10 millimeters and stopped firmly. If there was an egg at
the bottom, now it's an omelete 8-) I'll certainly keep an eye out for
more damage.

Searching via https://ipm.ucanr.edu/#gsc.tab=0&gsc.q=walnut%20borers&gsc.sort= turned up three candidates, flathead borer, shothole borer and twig beetles.
My best guess is shothole or flathead borer. All are commercial pests in California walnut groves and apparently the usual remedy is cultural: Keep trees healthy, remove damaged wood and sterilize the debris. The bugs are
here to stay amd a chemical warfare stalemate isn't very attractive, at
least not for an ornamental tree.

Out of seven trees in my walnut hedge only this one seems affected. Perhaps significantly, it also has the smoothest and likely thinnest bark. If one
tree is lost out of the seven that's acceptable attrition. Four trees,
evenly spaced, would provide ample shade when the city trees (Pistacia chinensis) come out, and I could be dead by then 8-)

Thanks for everybody's attention and thoughts!

bob prohaska

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Supersedes for wrong signature file.

[email protected] hat geschrieben:

David E. Ross <[email protected]d> wrote:

On 7/10/2025 10:48 PM, Michael Uplawski wrote:

Anyway. No chemical product exists which could act against an
ongoing infestation. Usually you have to get rid of the beetle.

There are actually two chemical methods of eliminating borers in trees.

I may have been quick with my writing. When I write “ongoing
infestation” I am influenced by my work in an orchard of about 7ha – whatever that is in imperial; let's say a big orchard of fruit
trees. “A tree” does not motivate the same reaction. But thank you
for the information.

I tried probing the holes with a wire, it went in, seemingly straight,
about 9 or 10 millimeters and stopped firmly. If there was an egg at
the bottom, now it's an omelete 8-) I'll certainly keep an eye out for
more damage.

Rather a grub than an egg, but this may be efficient. It is however
best to know your enemy. There are borers („drilling equipment” in
German, darned false friends), which do not harm the tree and some
are quite useful animals, when they are otherwise occupied.

… the usual remedy is cultural: Keep
trees healthy, remove damaged wood and sterilize the debris. The bugs are >here to stay amd a chemical warfare stalemate isn't very attractive, at
least not for an ornamental tree.

I do not know. If one tree is precious to me, I might try just
anything. Walnuts are terrific.

Cheerio

Michael
--
Geh Kaffee kochen

--- SoupGate-Win32 v1.05
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Supersedes for wrong signature file.

[email protected] hat geschrieben:

David E. Ross <[email protected]d> wrote:

On 7/10/2025 10:48 PM, Michael Uplawski wrote:

Anyway. No chemical product exists which could act against an
ongoing infestation. Usually you have to get rid of the beetle.

There are actually two chemical methods of eliminating borers in trees.

I may have been quick with my writing. When I write “ongoing
infestation” I am influenced by my work in an orchard of about 7ha – whatever that is in imperial; let's say a big orchard of fruit
trees. “A tree” does not motivate the same reaction. But thank you
for the information.

I tried probing the holes with a wire, it went in, seemingly straight,
about 9 or 10 millimeters and stopped firmly. If there was an egg at
the bottom, now it's an omelete 8-) I'll certainly keep an eye out for
more damage.

Rather a grub than an egg, but this may be efficient. It is however
best to know your enemy. There are borers („drilling equipment” in
German, darned false friends), which do not harm the tree and some
are quite useful animals, when they are otherwise occupied.

… the usual remedy is cultural: Keep
trees healthy, remove damaged wood and sterilize the debris. The bugs are >here to stay amd a chemical warfare stalemate isn't very attractive, at
least not for an ornamental tree.

I do not know. If one tree is precious to me, I might try just
anything. Walnuts are terrific.

Cheerio

Michael
--
Wrong computer, ignore signature

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[email protected] hat geschrieben:

David E. Ross <[email protected]d> wrote:

On 7/10/2025 10:48 PM, Michael Uplawski wrote:

Anyway. No chemical product exists which could act against an
ongoing infestation. Usually you have to get rid of the beetle.

There are actually two chemical methods of eliminating borers in trees.

I may have been quick with my writing. When I write “ongoing
infestation” I am influenced by my work in an orchard of about 7ha – whatever that is in imperial; let's say a big orchard of fruit
trees. “A tree” does not motivate the same reaction. But thank you
for the information.

I tried probing the holes with a wire, it went in, seemingly straight,
about 9 or 10 millimeters and stopped firmly. If there was an egg at
the bottom, now it's an omelete 8-) I'll certainly keep an eye out for
more damage.

Rather a grub than an egg, but this may be efficient. It is however
best to know your enemy. There are borers („drilling equipment” in
German, darned false friends), which do not harm the tree and some
are quite useful animals, when they are otherwise occupied.

… the usual remedy is cultural: Keep
trees healthy, remove damaged wood and sterilize the debris. The bugs are >here to stay amd a chemical warfare stalemate isn't very attractive, at
least not for an ornamental tree.

I do not know. If one tree is precious to me, I might try just
anything. Walnuts are terrific.

Cheerio

Michael
--
Geh Kaffee kochen

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On 7/11/2025 3:02 PM, [email protected] wrote:

David E. Ross <[email protected]d> wrote:

On 7/10/2025 10:48 PM, Michael Uplawski wrote:

[email protected] wrote in rec.gardens:

http://www.zefox.net/~bp/walnut/

[snipped]

Anyway. No chemical product exists which could act against an
ongoing infestation. Usually you have to get rid of the beetle.

[more snipped]

There are actually two chemical methods of eliminating borers in trees.

One involves a drench of Imidacloprid. The amount depends on the
diameter of the trunk at the height of your chest. The drench is
applied in the root zone. DO NOT use Imidacloprid while the tree or any
adjacent plant is blooming because it is very harmful to bees. On the
other hand, it is harmless to birds and mammals; thus, nuts from the
tree would still be edible.

Last I heard imidocloprid has been banned in California as of this
year (or thereabouts), at least for retail sale.

[snipped]

I read the regulation. It seems to make an exception for use of
imidocloprid on food plants. I have only used it on my dwarf citrus
when I see damage from leaf miners and on my peach tree to prevent
flat-headed bark borers.

The latest information on the Web from Agriculture and Natural
Resources, University of California, about citrus leaf miners still
suggests using imidocloprid. However, that Web page has not been
updated since 2021. You might want to contact your county's Agriculture Extension for clarification.

--
David E. Ross
Climate: California Mediterranean, see <http://www.rossde.com/garden/climate.html>

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