Birch leaves around Southcentral Alaska are turning brown, but it’s not fall foliage.

University of Alaska Fairbanks agriculture professor, Steve Brown, said it’s sawfly larvae causing the leaves to change color.

The larvae are known as “leafminers” because they burrow into the leaves and eat the nutrients for about two weeks before they fall to the ground.

Brown said it’s a natural occurrence, but it’s the worst infestation he’s seen for more than a decade.

He said the hot, dry summer weather likely weakened the trees and made them more susceptible to the bugs.

“It’s not as bad as it looks. It’s kind of like the tree gets the flu. It’s going to recover but it’s not going to be as strong as it was before,” Brown said. “Next year if we have good temperatures and good rain the trees will be fantastic.”

Brown said he’s taken a number of phone calls at the UAF Extension Service office in Palmer. He tells people there’s no insecticide that will prevent the larvae from taking over.

To protect a tree in your yard, Brown suggests plenty of fertilizer and water.

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