The Cully River Birch (Betula nigra ‘Cully’) is the least susceptible to the bronze birch borer. If you are planting or replanting, use this variety.
The best way to protect existing trees with little or no damage is to irrigate trees deeply at least once a month during dry weather. It takes two inches of water to reach the deeper tree roots. The best way to apply this is to lay a soaker hose in a circle under the outer reach of the branches. Let the water run for several hours, even overnight. A three inch organic mulch under trees is also effective. In addition to bark dust or bark chips, most arborists will deliver mulch chips from pruning at no charge.
Borer insecticides sprayed on the bark in May and June can prevent attack.
Control of infected trees
Since the larvae are feeding under the bark it is difficult to reach them with pesticide. The most effective way to reach the feeding larvae is by insecticide injection. Some arborists have injection equipment. Tree injection kits can be purchased online. Imidocloprid systemic insecticide such as Monterey Once a Year Insect Control can be applied as a drench around the trunk of trees. Tree roots absorb the insecticide and take it up to the inner bark of branches.