Maple with bark worms?

[Guffmeister]

Hi all,

I've got a Japanese maple which I've been growing from a small sapling over the last 10 years or so, and which suddenly died back quite drastically over the course of the summer. I had attributed this die back initially to the fact that I moved it into a nice protected corner of the garden, only for my neighbour's fence to blow down and create a wind tunnel effect. The whole canopy died back, but because I've been pruning it back systematically for the last two years to reduce its size and feeding it well, there were lots of small buds near the base that burst out in response - the only branches that survived were the ones below the wall beneath where the fence should be, which confirmed my suspicions that this die back was because of the wind. I was quite content that this was the reason, and because I had been trying to get the tree to back bud over the last few years this die back was oddly not too devastating since the plant has sent up new shoots from nearer the base of the trunk that would form the new tree canopy.

However...

I checked the tree the other day, and found the bark seemed to be falling away from the main wood. Again, I wasn't too concerned, as it was only on the dead branches, but I did notice that there was a patch of flaking bark that stretched right down to the base which was particularly wet and sodden. I was reluctant to mess with it too much, but I decided to peel it back. Underneath the wood was a load of worm-like creatures. They didn't look like beetle larvae or anything to me, so I'm trying to work out exactly what they might be.

Most importantly, I'm trying to work out whether these worm/larvae/things caused the die back that I saw in the summer, or are just taking advantage of the free dead bark. I guess the key is to understand what they are in the first place.

The next stage is what to do about it. If they're only eating dead bark then they won't be too much bother, but if they're burrowing into healthy bark I guess I had better try and get rid of them ASAP. Below is a picture of one of the dead branches with the bark stripped away and the worms exposed...



And below is one of the worms under the microscope.



I'm having trouble uploading other pictures for some reason, but I'll try and put some other pics of the tree.

If anyone has any ideas what these things are then I'd really appreciate it!

Cheers,
G

 

[Guffmeister]

So, here's a pic of the base of the tree, with the new growth that broke out over the summer. The branches are dead above this. I really like the nebari here, and hopefully I can introduce some interesting movement by doing something with these new shoots.

 

[Guffmeister]

...And this is the back, where the die back spread right down to the roots. Interestingly, the roots are pretty solid below this, with no sign of rot going down into the soil. It looks pretty ugly, but maybe it can be made into something interesting.

 

[0soyoung]

I would saw/chop the trunk safely (a few inches) above the obviously live shoots. I suggest that you then perform an 'autopsy of the trunk you've removed = saw it into chunks, split those chunks to see if there are any borer tracks, etc. At this point, it seems possible that the insects/larvae are a consequence of trunk death rather than the cause of it. This analysis will tell or at least be instrumental to figuring it out as well as assessing the likely future life of what you have left.

When the cambium of an acer palmatum dies, the bark over it just withers and desiccates. It usually turns blackish and weeps when the death occurs and over time dries and whitens. As the stem/trunk grows a bit, the added growth tends to lift the dead bark from the wood but will remain attached to the other 'live' bark, just as you found. In other words, this line of dead cambium that you recently discovered occurred before last season (at least as far back as winter 18/19, but likely earlier yet). This hollow space under the dead bark is a nice place for insects to lay eggs, should the adult have found a little opening in the desiccated bark.

Long term (5 years?) this area on your trunk base may be recovered or healed over by new bark. Meanwhile you can carry on with two options in mind:

1. choose the viewing front so that this 'scar' is hidden in back, out of view
2. choose to make it into a feature by hollowing out the tree (now or eventually).

That is, of course, assuming that your 'autopsy' indicates that the trunk base (that you wish to keep) is unaffected and likely healthy.

 

[Guffmeister]

Great! Thanks for your reply. I think that sounds like a good plan. I was reluctant to cut the tree until I knew which bits were dead, but now the bark is peeling it's quite easy to identify the dead bits and make sure I don't stress the remainder of the tree.

Hopefully this little maple will survive! It's actually got quite good proportions now all the leggy top growth has died back.

I'll post any findings later tomorrow!

 

[Tieball]

Burn or trash dispose of the branch and trunk pieces removed.
Google....White larva in tree bark. I think you’ll find lots of image candidates of what you have. And perhaps treatment options to further eliminate the problem.

 

[Forsoothe!]

I would begin a program of systemic insecticides, muy pronto.

 

[Handsome John]

Looks like fly larvae to me, the way its black head sinks back into the body is the main giveaway. Looks like a sliver of wood stuck in its body vs an actual head that a borer would have. I don't know of any of the fly species that's gonna attack a maple under the bark or attack a maple in general, so its most likely what Osoyoung said that is probably just flies looking for a damp place to lay eggs. I'd suspect it might be more of a fungal issue that attacked it. Its too bad was really shaping up to be a great tree.

 

[Guffmeister]

Looks like fly larvae to me, the way its black head sinks back into the body is the main giveaway. Looks like a sliver of wood stuck in its body vs an actual head that a borer would have. I don't know of any of the fly species that's gonna attack a maple under the bark or attack a maple in general, so its most likely what Osoyoung said that is probably just flies looking for a damp place to lay eggs. I'd suspect it might be more of a fungal issue that attacked it. Its too bad was really shaping up to be a great tree.

I'm hoping that too. The larvae don't have the characteristic look of beetle larvae, like a head section and leg-like structures, and I'm not aware of fly larvae that actively eat into healthy wood either. What could I check for to see whether it's a fungal issue? If 0soyoung is correct in saying the die back could have started in winter 2018/19 then it isn't as simple as my idea that it was just the wind that caused it. That said, the foliage looked as good as ever until I pruned it in late spring, so I didn't notice any weakness.

Thinking about it...it did suddenly die back after I pruned it. Could I have been an infection introduced from that?