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I have three birch trees in my front yard that I've been told have a bronze birch borer infestation, based primarily on the presence of numerous holes, each about 6-7 mm wide. There does seem to be some dieback at the crowns, but I don't know enough to tell if this is "normal" or indicates the trees are under severe stress.

Here's a picture of the three trees, you can see quite a bit of debris from the trees on the roof.

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A closeup of the trunks near ground level

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A detail of the holes, about 10 feet up one of the trunks

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Another detail shot, about 15 feet up one of the other trees

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Two arborists have said the trees are not salvageable, but I tend to discount "opinions" when there's an inherent conflict of interest (they're dying, and I'll remove them for you for $5000).

Question: Is it time to remove these trees?

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Birches in urban environments in North America have had a rough few decades thanks to birch leaf miner and the bronze birch borer. As this source indicates

The insect generally attacks weakened or injured trees, with a preference for very exposed trees. It therefore prefers trees in urban areas, sparse stands or harvest areas

This is what I observe from your pictures:

  • The garden soil around the trees looks compacted and it is probably drier next to your house than in a forest.
  • The trees are planted way too close to the house. In the event of a wind storm you could expect significant damage to your house if they fall on it.
  • There are too many holes in the trunk to be birch borer exit holes. The holes seem to be oval rather than the characteristic D shape They are more likely to be woodpecker holes due to them being mostly straight lines. The woodpeckers could be looking for insects but are more likely there for the sugar in the sap.
    • The die off at the top of the trees is characteristic of birch borer. I have seen many birch trees show this damage one year and are dead two years later.

I would expect that if you do nothing the birch trees will be dead in two to three years.

There is no need to remove them now as you can take some steps which might save them:

  • top dress the bed with compost twice a year
  • water thoroughly and frequently
  • fertilize: a 20:20:20 solution at 1/4 strength applied after a thorough watering in the spring growing season every year
  • cut out dead branches and incinerate to prevent the adults flying to new feeding areas. This should be done in early spring to late April depending on your area.
  • I rarely recommend pesticides but if you value these trees highly and don't mind the cost and overspray onto your house the Missouri Botanical Gardens recommends

Pesticides registered for use include: acephate (Orthene), azadirachtin (Bio Neem, Margosan-O), bendiocarb (Turcam, Closure), chlorphyrifos, imidacloprid (Merit, Marathon), and permethrin. Apply to the shoots and bark to kill adults and newly hatched larvae before they bore into the bark. Adults do not feed significantly on the leaves so it is not necessary to treat the foliage. Timing of insecticide applications is important because once the larvae bore into the bark they are out of reach of insecticides. First insecticide application should be when adults appear (look for the D-shaped holes) in early to mid-May. Frequently it is time to apply insecticides when bridal wreath (Spiraea x vanhouttei) finishes blooming. Some insecticides will need repeat applications so follow the label recommendations

Given the cost of spraying every year and that these birches have already begun to die back I would follow the first four recommendations. If the dieback continues have them removed and consider planting another type of tree or a resistant birch such as Betula Nigra, the black birch.

  • You can purchase imidicloprid as a drench, which you mix and pour around the trunk. Because it's systemic, it's taken up by the roots & spreads through the tree to the leaves. (It's a common insecticide against Emerald Ash Borer). The idea is that as the borers bore through the xylem and phloem, they take up the pesticide and die. Imidicloprid is a neonicitinoid, which just last week was finally tied (somewhat) to the reduction of honey & other bees. Because birch is wind-pollenated, it's unlikely the pesticide will harm bees-so long as you don't have flowers planted in the trees' understory. – Jurp Apr 24 at 23:07
  • @kevinsky Thanks for the detailed answer. I bought this house 3 years ago. I agree the trees are waaaay too close to the house, and they drop enough debris on the roof to require 3-4 gutter cleanings per year. Given that a significant number of birches in the area have been lost to borers, it really looks like these trees are just in the wrong place at the wrong time. I have decided to have them removed. – Jim Garrison Apr 27 at 6:08
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Those trees are goners. The holes are exactly what you see as the borer adult eats his way out of the tree. I have watched this personally; quite fascinating. I do wonder if those holes have been enlarged by a woodpecker though. What diameter are the holes?

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