AusBonsai

Can anyone help ID what has caused these holes in the trunk of this Prunus?
They rapidly appeared within 2 days. It looks like the tree has been hit with a 5mm drill bit.
I've dug around with wire but couldn't find anything inside. I then squirted metho in to exterminate the culprit. I'm undecided if I'll fill the holes or just let nature take its course.
Regards,
Steven

Wow! That's the worse case of borer I've ever seen! Definitely seal the holes. This will suffocate anything that might still be in there.
Spray the whole tree with a strong insecticide too. Carbaryl if you can get it. Let some soak into the soil as well.
Sometimes they start under the soil and come out on the trunk.

Yeah, I've had this on a few of my casuarinas about a year or so ago. I used WD-40 (it has that very long thin needle to get in all the way). I only sprayed for a microsecond, but it was enough to eradicate the problem.

I once sprayed one of the holes and soon after, the little borer wiggled out and I immediately killed it.

But wow that's a lot of holes you've got there Steven. I've only ever seen one hole on my trees, like a perfectly circular tube, going all the way down to the base.

Rory wrote:

the little borer wiggled out and I immediately killed it.

I suspect this is a different borer to the one I usually see which covers the holes with webbing and 'frass' (sawdust and caterpillar poo) and often starts eating around the surface of the bark before eating into the wood underneath.

Given that all these holes appeared suddenly I suspect they are escape holes where the insects have hatched and emerged to fly/crawl away and look for mates and new places to lay eggs. that will also explain why Steven can't find any residents in the holes - they have already fled the scene.

Sealing over the holes will allow the tree to heal over them quicker but if you want some character maybe leave them alone and see how things develop but it is always hard to predict the outcome.

given how many are/were in this tree it might pay to give your trees a systemic insecticide in case there are more lurking inside the trunks.

Interesting observation Neil!
I'll treat with an insecticide ASAP.
Thanks,
Steven

Hi Steven...This was one of the casys with the same signs....

With this tree, I used the WD-40 for about one-fifth of a second. It never presented any further problems so I don't know whether this hole had been evacuated prior, or whether it actually killed the borer, but either way it has not had a problem since. This one was about a year ago I recall.

I had the same in this fig.

When I sprayed some water into the hole a small brown frog poked his head out so I didn't have the heart to seal it.

We now call this tree the Frog Fig!

Hi Steven,
Thanks for posting this. It's been good to read what others have had to say. These holes are quite large, Steven has described them as 5mm holes. My concern in a situation like this is ROT. They are big enough holes to allow water to fill. If it was my tree I would treat it with the insecticide, allow the holes to dry for a couple of days and seal them.

Regards Ray

Hi Ray,

So, should I try to kill the frog first or just entomb him alive?

Ray M wrote:Hi Steven,
Thanks for posting this. It's been good to read what others have had to say. These holes are quite large, Steven has described them as 5mm holes. My concern in a situation like this is ROT. They are big enough holes to allow water to fill. If it was my tree I would treat it with the insecticide, allow the holes to dry for a couple of days and seal them.

Regards Ray

I can see why you would say that. In my case all the holes on the trees go all the way to the roots. I believe the critter(s) started in the roots and munched upwards and outwards, or then just lived inside the hole and took other routes of munching. Rot is not a problem for me, as the water doesn't pool and just disperses downwards into the root system.

However over time if enough material / soil was to collect inside at the base of the hole, then this could present a problem with rotting. I might have to agree. Also its only a guess that there aren't side funnels from the main hole that stop before the root system, thus they could be pooling water. I hadn't thought of that possibility.

hard1all wrote:Hi Ray,

So, should I try to kill the frog first or just entomb him alive?

I'm sure you could find a way to encourage him/her out. Put a bowl of water, he/she might come out for a swim.

ooops, too late I'm afraid

and I ruined a couple of kebab skewers in the process

oh well!

My best guess would be elephant weevel. We have them at work and the hole looks very much the same. They normally attack weak plants in general. The theory is that a strong plant has a lot of sap flow which make it unpleasant for the weevel. A weak tree with low sap flow means the weevel can eat around withoit being drowned or stuck up with sap. Just a guess may be something different.