Answer: The surest way is to plant a birch that's resistant to the bronze birch borer, says Jim Appleby, forest entomologist at the University of Illinois in Champaign. A good choice is our native river birch, which can tolerate wet and heavy soils. Heritage is a long lived cultivar that's very similar to the white birch. Ordinary river birch has a pale copper to gold bark color, but Heritage is very nearly white. The bronze birch borer is a major problem on European white birch, says Appleby. The adult emerges in spring after overwintering on the bark as a larva and lays eggs in cracks and wounds in the sunny side of the trunk and main branches. The eggs hatch and larvae bore into the tree, often killing it within three years. The borer thrives on weakened trees, so plant white birches in rich, well drained soil, feed them each spring with a complete fertilizer, mulch with three to four inches of bark around the drip line and, most important, make sure the trees get at least one inch of water a week, he explains.
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