Many birch leaves in Fairbanks and Anchorage are going from green to brown as the result of an insect infestation. U.S. Forest Service entomologist Stephen Burr in Fairbanks says a leaf mining bug believed to have come to the state on imported ornamental trees, is to blame.
“The amber-marked birch leaf-miner,” Burr explained. “It’s an invasive sawfly, which is a primitive species of wasp. They’ve been in Alaska for over 20 years, but have only really started to hit the Fairbanks-Northpole area really badly in the last few years.”
Burr says the larval stage of the wasp feeds on birch leaves.
“The wasps are laying their eggs inside the leaf, and then the larva hatch and are feeding inside the leaf, mining it, which is where you get the ‘leaf-miner’, eating inside,” Burr said. “And that causes those brown blotches that you see on the leaves.”
Burr said the leaf damage does not hurt the tree, and the only real casualty is the loss of normally beautiful fall birch foliage.
“Aesthetically, it’s very ugly,” Burr said. “It’s definitely not as beautiful as the yellow you would normally get, birch change. So it’ll affect the aesthetics, but that’s about it.”
Burr said it’s unclear why the leaf miner infestation, which is believed to have originated in Haines and moved to Anchorage and now Fairbanks, does not appear to have spread into remote areas.
Dan Bross is a reporter at KUAC in Fairbanks.
