Birch Leafminer

The Birch leafminer's are caterpillar-like larvae of tiny sawflies that mine birch leaves. 

What are the Risks?

The birch leafminer mostly causes aesthetic damage to birch trees, such as:

• Brown patches on birch leaves
• Leaf appears hollow
• Black larval excrement can be seen

Repeated attacks may weaken the tree and make it more susceptible to attacks by other insects.

What to Look For

• Adults are about 1/8 inch long, and are black and fly-like
• Larvae are yellowish white and grow up to 1/4 inch long
• Early mines created by leafminers look like light green or white discolorations on the leaves
• A simple way you can check for larvae is to hold suspected leaves up to the sunlight. If you notice partial or whole areas of the leaves that are consumed, it is a good indication you may have birch leafminers

Prevention

Here are some ways you can help control the birch leafminer in your trees:

• Monitor birch trees closely in the spring
• Track bud break in your tree to help predict the feeding time of the leafminer
• The best time to treat the birch leafminer is when the larvae hatch inside the leaves and begin to feed

Related Links

• Birch leafminer - Natural Resources Canada
• Birch leafminers - UMN Extension