Late Birch Leaf Edge Miner Damage

Observation by Nick Treinen:

Birch leaves all throughout the Mat-Su valley have recently been showing signs of infestation. Most birches on Lazy Mountain seem to be affected.

This is significant also in connection with the spruce bark beetle epidemic. The two dominant boreal trees in this area (birches and spruce) are both suffering significant insect infestations. This comes during the hottest summer on record and an exceptionally dry summer as well.

Jessie Moan with the University of Alaska Fairbanks Cooperative Extension Service writes:

Based on the picture submitted, the damage looks more like late birch leaf edgeminer (Heterarthrus nemoratus) than ABLM (amber-marked birch leaf miner) (Profenusa thomsoni). Based on recent ground surveys the majority of the damage that is being observed in Southcentral Alaska is due to late birch leaf edgeminer feeding.

Comments from LEO Editors:

According to the US Forest Service (USFS), amber-marked birch leaf miner (Profenusa thomsoni) and late birch leaf edge miner (Heterarthrus namoratus) are the two birch leaf-mining sawfly species found in Alaska. Both are invasives and inhabit alders (Alnus spp.) and all native Alaskan birches (Betula spp.), but their damage doesn't really harm the trees they infest. Thus far, there hasn't been any record of birch mortality caused by these flies. Their distribution range in the state is mainly between Southcentral and the Interior. Source: USFS Forest & Grassland Health -- Invasive Birch Leaf Miners webpage. Sarah Ingram