Diario del proyecto Alaska Forest Health Observations

Have you noticed the birch leaves yellowing a bit early this year? Check out this press release from the US Forest Service regarding the current birch leafminer outbreak in Alaska: https://www.fs.usda.gov/detail/r10/news-events/?cid=FSEPRD1057235

FAIRBANKS, Alaska – Aug. 30, 2022 – Birch tree leaves in Interior and Southcentral Alaska have turned brown prematurely due to an ongoing outbreak of two birch leafminer invasive species, the amber-marked birch leafminer and the late birch leaf edgeminer.

As larvae, birch leafminers live in and eat the insides of birch leaves, causing them to turn yellowish-brown and prematurely drop before the fall season. During an outbreak, up to 90 percent of the leaves on a tree can be defoliated. The extensive defoliation by the larvae has resulted in browning birch tops observed in hillsides and along roadways, which has raised concerns about a hastening to fall as well as public concern for the state of birch trees in outbreak areas.

Residents may soon notice large amounts of larvae on the ground near birch trees or collecting on property sitting under birch branches. After summer feeding, birch leafminer larvae drop to the ground, and spend the winter in a cocoon, emerging as adult sawflies the following spring.

Damage by birch leafminer is primarily aesthetic and tree death has not been observed in Alaska so far. Repeated damage, however, can result in declining tree-growth rates and weakened trees that are susceptible to damage by secondary diseases and forest pests.

Forest visitors can help the Forest Service track the birch leafminers by uploading photos, video, or information on sightings or damage to iNaturalist.com, which will automatically be included in the Alaska Forest Health Observations Project, a citizen science project in iNaturalist. More information on the project can be found here.

For more information visit the Forest Health website.

Alaska’s National Forests – where nature, people, and tradition come together. Follow Alaska’s National Forests on Facebook and Twitter. For a wealth of information about the Alaska Region, visit our media toolkit.

USFS press release regarding the current blackheaded budworm outbreak in Southeast Alaska: https://www.fs.usda.gov/detail/r10/news-events/?cid=FSEPRD1057047

JUNEAU, Alaska – Aug. 29, 2022 - Residents and visitors may notice a lot of small brownish-gray moths fluttering around. Western blackheaded budworms are transforming from voracious caterpillars into moths and are emerging throughout the area. These caterpillars, which were abundant in July and August, are responsible for causing the needles on hemlock and spruce trees to turn reddish-brown.

Not to worry - while heavy concentrations of feeding activity from western blackheaded budworm caterpillars can lead to the loss of trees, most will recover. The forest may look different following an event of this size, but these defoliator outbreaks have happened before, and the forests will benefit in the long-term through sunlight breaks in the canopy and fertilization from droppings and half-eaten needles. Additionally, the caterpillars are a food source for hungry birds and fish.

The current outbreak began in 2020 in the central Tongass area and then expanded across southeast Alaska, reaching as far north as Haines and as far south as Ketchikan in 2022. Western blackheaded budworm outbreaks typically last 2-3 years before ending naturally.

Forest visitors can upload photos, video, or information related to sightings of the insect or its damage to iNaturalist.com, which will automatically be included in the Alaska Forest Health Observations Project, a citizen science project in iNaturalist. More information on the project can be found here.

The last time a major western blackheaded budworm outbreak in the southeast took place was from 1992 to 1995.

For more information visit the Forest Health website. Alaska’s National Forests – where nature, people, and tradition come together.