The Q&A Archives: Replacing a Birch tree with one that is borer resistent

Question: We recently lost a twenty year old 40 foot white birch tree to bronze birch borers. It took three years to fatally damage the tree. I have noticed many other green leaf birch trees in the neighborhood are also suffering from a slow death. I have a black leaf birch in the back yard that is currently totally untouched by these pests. There are five green leaf weeping birches in close proximity to the black leaf birch and they are showing signs of die off at their tops. Is there any type of birch tree that is completely resistant to this pest? I have been to many nurseries in the area and they do not know where to get the black or purple leaf variety of tree. Is it safe to plant a birch tree in the same place where you have removed a sick one? We have completely removed the stump and roots and replaced the top 2 inches of the surrounding soil and added fresh amendments. I would hate to go to the trouble of planting a new birch tree and have it suffer the same fate. Any suggestions?

Answer: Though they do not have pure white bark, river birch (B. nigra) is quite resistant to attack and gray birch (B. populifolia) is moderately resistant. However, gray birch is very susceptible to leaf miners and river birch is attacked by leaf aphids. Probably the best species is the Monarch birch (B. maximowicziana) which has white bark on older trees and is only moderately susceptible to leafminers and aphids.

As with most wood boring insects, the bronze birch borer is extremely difficult to control, especially if an infestation is established. This pest seems to prefer birches located in unsuitable habitats. Birches generally grow in shady, cool and moist wooded areas. Thus, when birches are planted as an accent plant in sunny, dry urban lawns, they are rapidly attacked.

If you decide to replant a birch, keep the soil moist, fertilize regularly and control aphids and leafminers to help keep your birch vigorous and better able to withstand borers.

I can find only one source of these trees in California: Sonoma Horticultural Nursery in Sebastopol. Perhaps a phone call to them can lead to a source closer to your home. (707-823-6832).

Best wishes with your landscape!

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