Eliminate Birch Leaf Miners with Regular Treatment

The birch leaf miner is one common pest that attacks Birch trees in the United States and Canada. While these pests do not kill the trees, they do kill a tree’s leaves. This can be devastating for the trees, making them susceptible to other pests and reducing their aesthetic value.

What Happens When a Birch Is Infected?

Trees are first infected shortly after budding when birch leaf miners (adult sawflies) lay eggs on the growing leaves. Within 10 days of the initial budding, the new larvae begin to mine the leaves of infected trees. Leaf miners will go through about two life cycles during the summer, causing progressive damage to the tree. If your trees become infected by leaf miners, here’s what
you’ll see:

  1. In June, damage will first be seen as larvae and their waste begin to appear on affected leaves. The result will be white and black spots forming on the surface of the leaf.
  2. After 5-6 weeks, larvae will drop to the ground to pupate. Adults will emerge about two weeks later. By this time, leaves will have larger black waste spots and show active signs of decay. Leaves will turn brown and become brittle.
  3. These newly developed adults will immediately lay eggs. The second generation of leaf miners is less problematic, as only new leaves can be infected. Of course, if the tree tries to regrow its leaves, the second generation will be more potent.
  4. If left untreated, trees can lose large amounts of leaves and become infected by other pests like the bronze birch borer.

How Are Birches Protected?

It’s best to use systemic pesticides like acephate every 24 months as trees are budding—contact pesticides should not be used. You should not use pesticides on transplanted trees, as this can cause significant damage to them. Giving a tree the proper amount of water, nutrients, and fertilizer can keep it strong during an infection and prevent further damage.

Trees are large investments that need to be protected from pests like the birch leafminer. If you have any other questions regarding leafminers or other tree care questions, visit our Plant Management page or contact us toll-free at 1-877-444-8733 (TREE).You can also fill out our estimate request form today!