What makes holes in walnut trees?

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.

snipped-for-privacy@www.zefox.net wrote in rec.gardens:

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

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

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.

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

Perhaps AceCap? It's banned in California also.

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

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

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.

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.

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

Cheerio

Michael

Supersedes for wrong signature file.

snipped-for-privacy@www.zefox.net hat geschrieben:

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.

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.

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

Cheerio

Michael