Alaska Forest Health Observations 2020's Journal

September 16, 2020

Foliar tar spot fungus (Rhytisma arbuti) on rusty menziesia

Have you seen black spots on false azalea/rusty menziesia? Plentiful rain in SE Alaska has led to an abundance of the foliar tar spot fungus (Rhytisma arbuti). It doesn’t do much damage since it occurs after seedset. For more information visit:

Posted on September 16, 2020 15:49 by awenninger awenninger | 0 comments | Leave a comment

Spruce beetle update (Dendroctonus rufipennis)

The Mat-Su region continues to experience extensive spruce tree mortality due to a spruce beetle outbreak. #AKForestHealth scientists from Anchorage & Fairbanks visited the region to view the area & discuss the health of the forests. For more information, visit

Posted on September 16, 2020 15:37 by awenninger awenninger | 0 comments | Leave a comment

Rusty Tussock Moth (Orgyia antiqua)

Rusty tussock moth caterpillars feed on understory trees and shrubs throughout AK. The males have been flying in great numbers near Talkeetna and Hatcher Pass (the females are flightless). If you notice these critters, post your observation to iNaturalist!

Posted on September 16, 2020 15:33 by awenninger awenninger | 0 comments | Leave a comment

August 14, 2020

Petiole galls on Balsam poplar/cottonwood

Galls formed at the base of balsam poplar leaves can be found throughout the state. Within these galls can be found numerous aphids of the Pemphigus genus. They lack the cornicles (terminal abdominal tubules) characteristic of other aphids. When eggs hatch in the spring, these aphids begin feeding on leaf petioles which induces the production of galls that envelopes and protects the developing aphids. As they mature, winged aphid forms will emerge from these galls. While we wait for genetic identification of the species in Alaska, similar species in North America will leave their galls and colonize a different host mid-summer, where they will continue to feed and reproduce throughout the season. By the end of the season, females will return to Populus spp. trees and lay a single egg that will overwinter and emerge in the spring. You can help the Forest Health Protection better understand the range of these aphids by uploading your observations and pictures of these galls to iNaturalist.

Post created by @DanaBrennan

Posted on August 14, 2020 16:01 by awenninger awenninger | 0 comments | Leave a comment

June 24, 2020

Hardwood defoliation near Cooper Landing, AK

Areas of heavy hardwood defoliation were found along Juneau Creek Road near Cooper Landing. Dark-colored caterpillars were found on aspen, birch, willow, cottonwood and wild rose. Some understory aspen had very little leaf surface remaining beside leaf midribs.

These caterpillars appear to be pupating at this time and will possibly emerge as adults in the fall. You can help the Forest Health Protection team track these types of outbreaks by uploading your observations and pictures to iNaturalist.

For more information on Alaska Forest health visit:

Posted on June 24, 2020 23:10 by awenninger awenninger | 0 comments | Leave a comment

June 19, 2020

Western tent caterpillar (Malacosoma californicum)

Have you noticed any of these caterpillars and ‘tents’ in alder or cottonwoods? They have been reported in Ketchikan and the Forest Service State & Private Forestry would like your help to determine where they occur. If you notice western tent caterpillars, take a picture and upload it to iNaturalist to help us collect data on these forest pests.

Posted on June 19, 2020 15:53 by awenninger awenninger | 0 comments | Leave a comment

June 01, 2020

Green alder sawfly (Monsoma pulveratum) overwintering under bark of beetle-killed spruce

Beetle killed trees can become homes for other forest pests, like these green alder sawfly pupae on a white spruce. Adults will soon emerge & lay eggs on nearby alder, where larvae will hatch & start munching.

Posted on June 01, 2020 15:30 by awenninger awenninger | 0 comments | Leave a comment

May 29, 2020

Spruce beetle (Dendroctonus rufipennis)

If you haven’t seen me yet, you soon will. As temperatures start to rise you’ll see my small reddish brown to black cylindrical body (1/4" long by 1/8" wide) as I look for a new home in a nearby spruce tree.

Have you noticed red sawdust at the base of a tree? This is the result of spruce beetles boring into trees-other insects also bore into trees, you may be able to id the type of beetle by sawdust color & location.

Posted on May 29, 2020 18:43 by awenninger awenninger | 0 comments | Leave a comment

May 27, 2020

Introducing Alaska Forest Health Observations 2020

Is there something “bugging” a tree in your area? Add a picture of your observation to the iNaturalist app! USFS Forest Health Protection is monitoring forest insect & disease observations & can help id forest health concerns.

Posted on May 27, 2020 16:09 by awenninger awenninger | 1 comment | Leave a comment