What’s killing this Betula Utilis

Question

A client of mine has 3 Betula Utilis very close to each other and one is dying. We’ve discovered some bug which it appears to be eating it from the inside. Any ideas what this is?

Answer 1

Is that Cardiff in Wales UK?

You say you discovered a bug, but did you see an adult, or larvae in the tree or what was your process of discovery? Do you have a photo of the bug? What are the signs of damage besides the bark discoloration, hole in the wood and associated wood decay? Are there exit holes in the bark, die-back in the top, galleries where larva are feeding/tunneling? Or only the local decay? These would be important observations to help us identify a pest. Or could it be from wounding and wood decay fungal infection without a pest present?

No bronze birch borer in UK yet as far as I know. Hope you aren’t the first. It is hell on drought stressed birches in my home state of California.

https://www.forestry.gov.uk/bronzebirchborer

Consider other borers, like Asian Longhorn beetle:
https://www.forestry.gov.uk/asianlonghornbeetle

If you suspect beetle borer activity, chemical control is usually not effective for an active infestation. But preventive treatment is important for protection of trees that are not yet affected.
Systemic insecticide like the neonicotinoid “imidacloprid’ is applied appropriately as a soil drench in fall for protection the following spring and summer, or applied in early spring, is a standard preventive treatment for bronze birch borer. I also do whats called bark banding or trunk banding with a pyrethroid insecticide barrier that has a long residual effectiveness. A common banding treatment is permethrin or bifenthrin at the highest label rate, sprayed on the bark of the woody stems to achieve several months of protection from new borer entries.

Answer 2

But of course the most important pest management measure is to keep the trees as healthy and resistant as possible with good soil and water management. As with many tree species, birch are more susceptible to pest and disease issues if they are physiologically stressed from water deficit or nutrient deficiencies.

Answer 3

Thank you for taking the time to answer this DrTreeLove, it’s greatly appreciated. I’ve asked my client for some info on the tree, unfortunately I’ve moved away and can’t pop around to see the tree. He’s been very vague and seems like he’s not bothered. It doesn’t sound like borers, just some very small insects aphid size were spotted near the rot apparently. It has been a very dry last few months after a very wet winter so maybe this has something to do with it. I dont think they’ve been keeping on top of the watering which won’t help.