Bug Infestation, what now?

ONe of my elms i collected last year has a large root (3-4" approx.) that I had planned on cutting off next year. While looking at it today I appeared dead. I pulled at the bark and it easily came off and underneath was a maze of insect tunnels. After closer investigation I found lots of tiny white grubs on the wood just beneath the soil. My question is what do I do now? Should I repot in clean soil and cut the bug ridden root off. I happened to order some plant propagation heating pads that should come in anytime. Would that help the tree make it to spring if I do repot now? I tried to take a pic of the grubs put my camera would not focus that small, but here is the tree and the big ugly root.

Elms are a favorite species of bark boring beetles, who's eggs are laid into both living and dead wood and then hatch and eat interesting patterns out of the phloem as they mature. The fact that you have had an attack indicates your trees weekend state as it is easy prey as it were..I would cut that root off now back to living wood, paint the wound, and re-pot into 100% inorganic medium.

Unfortunately the species that tend to prefer Elms (S. acolytes and Hylurgopinus ruffles) also often carry the fungus that causes Dutch Elm disease. You can try systemics if it makes you feel better but the presence of bark borers on a collected Elm is a bad sign, I would begin to emotionally distance myself from the tree at this point, if you have other Healthy elms seriously consider ditching this specimen, yes its that serious, if you have a host tree with elm borers reproducing in it you risk other elms around you.

Personally if that tree were in my collection it would find itself on the fire. No joke.
What species of Elm is it?
-Jay

Dang this sounds bad. Its a winged elm. I lots two small ones last summer, Im guessing from the same thing. Is there anything I can treat my trees with to prevent this in the future. Only been growing treats for three years now and have never treated trees with insecticide or herb.. I guess I should start, any suggestions for a rookie.

Looks like typical die back from the large cut on the root to me. Once the cambium dies back and the bark gets wet, the gap can play host to all manner of beetle larvae. We in the UK have Dutch Elm disease all around us but it is unheard of in bonsai cultivation as far as I am aware. Dutch Elm is a Top down disease anyway. I would treat the tree with a systemic pesticide a couple of times and move out to a secluded area for a while.

The reason Bonsai tend to stay clear of dutch elm is that their diminutive size tends not to attract the attention of the beetle. But wild harvested trees of any decent caliper as this one is, should be treated with caution.

In my landscaping and in my bonsai work I deal with Ulmus americana and the primary way to keep DED at bay is pruning in winter (when the adult beetle is not flying) and painting every wound no matter how small. I have a nice American Elm growing through a hole I cut in my deck and I keep it at 15 feet. At about 25-30 feet they grow thick enough to be of interest to the beetle, who may infect them, they die from the top down as Will says, and re-sprout from the unaffected roots and the cycle begins again...what a terrible way to live.

A bonsai can always be treated conveniently with a systemic of course but often by the time you notice the evidence of DED infection, you will be needing to prune away major portions of your canopy to help keep the disease from spreading. Large trees in nature or in gardens can only be treated with major limb removal, although I have known of brave Arborists who actually inject fungicides directly into the crown of large specimen trees in a valiant attempt to keep them alive.

Winged elm may be more resistant but if they have it, they have it, and the stress of continually fighting off the spreading fungus strangling the vascular tissue makes the additional stress of bonsai culture unwise. I hope this is just rot and beetles...thats a fine piece of material, with elms seal everything you cut very well and keep them extra vigorous!
-Jay

With Ulmus being one of my favourite subjects for bonsai, I have heard and read many theories as to why Elms become infected with DED at a particular size. One particularly far fetched theory was that the Elm beetle only flies at 15 feet. This is probably fine where I live as it is relatively flat but visions of these beetles ploughing Kamikaze style into small hills makes me chuckle
Elm reduced to hedging does extremely well around East Anglia and only gets into trouble when left to its own devises. At around 15-20 ft, top branches turning brown in the height of Summer are the first sign that the beetle is in. As Jay mentions, at this size of tree the bark is sufficiently thick for the beetle to breed and the mass of foliage emits enough of an odour for the beetle to sniff it out. Once the female starts to burrow and lay eggs, this damage sets off pheromones that attract many more beetles and the tree then has little to no chance of survival.

As well as a systemic Insecticide, you may want to try a fungicide as well. Good luck and I hope it all works out well.

Thanks guys for the input. I cut off the big dead root and will treat with a systemic tomorrow.

Wish me luck.

FEZ wrote:Thanks guys for the input. I cut off the big dead root and will treat with a systemic tomorrow.

Wish me luck.

I think systemic works better when the tree is in active growth, that makes sense to me but it might be workable now too. Someone will know better than me I'm sure,

seal that cut very well! I imagine that left a mighty wound. Wood hardener/preservative might be in order
-Jay

I would not rule out termites -- especially in the dead wood.

A systemic won't do a lot this time of year, A pyrethrin spray should help.