---

Not long ago my son and I were talking on the patio next to one of our paper birch trees. All of a sudden he pointed to some unusual insects stuck in the wood of the tree and they were tough to dislodge due to the penetration. I took one of them to my insect book and looking under tree insects, found it was bronze birch borer.

Adult borers are slender, metallic-coppery beetles about three-eight inches long, although all of these were more than a half an inch long. We were lucky to have spotted them because they are rarely seen.

They are in the family Buprestidae and are often termed metallic wood boring beetles. Larvae are underneath the bark and are white, segmented, legless grubs with an enlarged area behind the head. This gives the name flatheaded borers.

All birch species can be attacked but some are more susceptible to birch borer than others. European white birch, silver birch, and the weeping birch are most often attacked. The paper birch, which was the species we noticed the borer on and the canoe birch are among those that are moderately attacked by the borer. The river and red birch are among the species that are least often attacked by the bronze birch borer.

Since noticing the problem, I thought back to other birch trees where parts of the tree died and we cut it down, thinking it had died of old age. The larvae of the birch borer feed just beneath the bark. This feeding girdles the phloem, reducing the amount of food that goes to the upper part of the tree. Foliage on branches in the upper crown begins to yellow in midsummer causing brown and dead leaves. Ridges begin to appear on the bark of the trunk and larger branches. D-shaped exit holes where the adult borers have emerged from the tree begin to appear on the trunk and larger branches.

The birch borer over- winters in the tree as a mature larva and hatches in the spring. Adult beetles begin to emerge from late may to early June and begin to feed on leaves and mate shortly after they appear. Female beetles lay eggs in bark cracks and crevices and the tiny larvae appear in about a week. The zigzag patterns are evidence of their feeding and the cycle goes on.

There are some things that can be done to reduce the problems with the bronze birch borer. Select an appropriate location for your birch tree. Birch trees like soil that will remain cool and moist but where the tree will receive full sunshine for most of the day. Choose birch like the River Birch, Heritage River Birch, Yellow birch, or Sweet Birch that have less trouble with the birch borer. Proper maintance is important also. Birch trees don't like dry soil conditions. Mulch two to three inches deep over the roots to keep them cool. Fertilizer only if nutrients are deficient and don't prune from May 1 through July 1.

Use chemical only if there are symptoms of borer activity.

Insecticides can be applied to the bark and foliage of trees to prevent new attacks. Any treatment should be applied by a professional applicator.

Also, treatment is not recommended for trees that are heavily infested or near death.

---