Bronze Birch Borer

Agrilus anxius

Bronze birch borer, Agrilus anxions, is a native wood boring beetle that attacks birch trees that are stressed by drought, soil compaction or other insects. Birch trees prefer cool, moist locations which are not often found in residential or urban areas, therefore many urban birch trees are at risk of bronze birch borer attack.

Download Bronze Birch Borer Fact Sheet

Treatment Strategy

Understanding that bronze birch borer only attacks stressed trees helps us design a treatment program that both alleviates the stress and helps the tree with its defense system. In addition to cultural practices such as watering, there are preventative and therapeutic insecticide treatments that are transported through the conductive tissues of the tree.

Soil applied systemic insecticides such as Xytect and Transtect offer protection from bronze birch borer by killing larvae in the stem and trunks as well as adult beetles feeding on the leaves.

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Bronze Birch Borer Treatment Option 1

Cultural Practices

Watering

Adequate water is a key factor in maintaining healthy birch trees. A slow, deep watering event once every few weeks during dry conditions will help maintain soil moisture levels and minimize the stress that invites the bronze birch borer.

Mulching

Mulch is very beneficial for birch and all trees because it reduces competition with turf and moderates soil temperature and moisture levels. The addition of 3 inches of wood chips or shredded bark under the drip line can have a very beneficial effect by holding in moisture and promoting healthy fibrous roots.

Fertilizing

Proper fertilization can be beneficial for any tree. However, it is important to know that research shows that too much nitrogen will increase your birch trees susceptibility to Bronze birch borer, by increasing succulent growth. Do not fertilize birch trees that are showing symptoms of bronze birch borer, especially if water is limiting their growth.

Application Type - Cultural practices

DIY Equipment Needed:

•  Soaker hose (for watering)

•  Mulch

• Rake and shovel

• Low nitrogen fertilizer

Bronze Birch Borer Treatment Option 2

Using Insecticides

Preventative Treatments

Important trees that are not yet showing symptoms or those that have been severely compromised by drought or construction can be treated annually to prevent symptoms. Xytect is applied each year, preferably in the spring or fall and lasts one full year in the tree. Mid-summer applications can be done but are not optimal.

Application Type - Soil drench

DIY Product/Equipment Needed:

• Xytect

• Soil Drench Kit

• Measuring or diameter tape

• Measuring cup

• Bucket or watering can

• Gloves

Bronze Birch Borer Treatment Option 3

Therapeutic Treatments

Trees that are showing bronze birch borer symptoms in less than one third of their canopy are still good candidates for treatment. Once an infestation progresses beyond this point, the conductive tissues are too compromised to get insecticides into the tree. Dead branches will not grow back and should be pruned out.

In order to effectively control a heavy infestationcanopy loss) two treatments are required in the first year. The first needs to be fast acting to kill the larvae that are in the tree. Transtect is a quick absorption insecticide that effectively controls borers and will move into your tree in about a week. Following up with a Xytect application will provide one full year of protection. Annual Xytect™ applications will maintain this protection with no need for additional Transtect™.

Application Type - Soil Drench

DIY Equipment/Product Needed:

• Transtect

• Xytect

• Soil Drench Kit

• Measuring or diameter tape

• Measuring cup

• Bucket or watering can

• Gloves

Bronze Birch Borer DIY Kit

Option 1

Application Type – Cultural practices

DIY Equipment Needed:

•  Soaker hose (for watering)

•  Mulch

• Rake and shovel

• Low nitrogen fertilizer

Option 2

Application Type - Soil drench

DIY Product/Equipment Needed:

• Xytect

• Soil Drench Kit

• Measuring or diameter tape

• Measuring cup

• Bucket or watering can

• Gloves

Option 3

Application TypeSoil Drench

DIY Equipment/Product Needed:

• Transtect

• Xytect

• Soil Drench Kit

• Measuring or diameter tape

• Measuring cup

• Bucket or watering can

• Gloves

How Is It Spread?

Just like most wood boring beetles, it is the larval stage of bronze birch borer that causes damage. The larvae feed on the sapwood of the tree, disrupting the flow of water, nutrients and sugar. Trees may be infested for several years before they begin showing visible symptoms.  Preventative treatments are typically required to maintain birch tree health, especially as they mature.

Susceptible Trees

All birch trees are susceptible to bronze birch borer attacks, however river birch trees are among the most resistant.

Symptoms

• Yellowing of leaves, just below dead tips of branches.

• Thinning leaves and branches at the top of the tree.

• Top-down dieback, occurring in the upper third of the tree first, showing yellowing then death.

• D-shaped exit holes. Bronze birch borer is a flat-headed borer, so when it emerges as an adult it chews a distinctly D-shaped hole.

• Swelling where larvae have tunneled underneath the bark.

Lookalikes

Drought; construction injury.

Related/Similar Problems

Drought, soil compaction, birch leafminer

Timing

Spring or Fall

Urgency

High

Risk of Spreading

Moderate

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