The best prevention for bronze birch borer on a silver birch is a healthy, unstressed tree, which TreeHelp's guidance says comes from proper watering and fertilization. In practice that means deep, regular watering, a layer of mulch, pruning only in late fall or winter, and slow release feeding.

Why is silver birch so vulnerable to bronze birch borer?

Because it needs constantly moist, acid soil and is sensitive to heat stress, and a drought stressed birch is more susceptible to the borer. European white birch, another name for silver birch, is highly susceptible to the beetle.

How should a silver birch be watered to resist borers?

Deeply and regularly, moisture reaches 24 to 36 inches into the root zone, especially through hot, dry spells. A 2 to 3 inch layer of organic mulch around the base holds that moisture in and protects the shallow roots.

Slow release openings that let water seep out over several days are the core of the Treegator Original Slow Release Watering Bag, which zips around a young birch trunk 1 to 8 inches across and is refilled once or twice a week.

When should a silver birch be pruned?

Only in late fall or winter. Open pruning wounds attract bronze birch borer during the growing season, and a birch pruned in spring bleeds sap.

Does feeding a silver birch help keep borers away?

Yes, as long as the feed is slow release, because a quick hit of nitrogen forces soft, weak growth that attracts the borer. Rather than a quick release lawn feed, TreeHelp Premium Fertilizer: Birch is placed below the grass roots near the drip line once or twice a year, away from the trunk.

Frequently Asked Questions

Where should a new silver birch be planted?

In full to partial sun, with protection from hot afternoon sun, and in moist, acid soil.

Is silver birch a good choice in a warm climate?

Usually not. It grows in zones 3 to 6 and is short lived unless grown in the North with plenty of moisture.

Should mulch touch the trunk?

No. The mulch is spread around the base but kept from piling up against the trunk itself.

Can an insecticide add another layer of protection?

Yes. A once a year soil drench can protect a healthy birch for 12 months, as the guide to controlling bronze birch borer in birch explains.