Abundant Aphids and Defoliator Attack

Observation by Brandi Radigan:

We have never seen so many aphids and holes in the leaves on the trees as we did this summer!

Jason Moan, Forest Health Program Manager at the Alaska Division of Forestry, writes:

I’ve seen aphid activity this year associated with a variety of different plant species. The holes in the leaves though, are not aphid-caused. Those holes are more likely the result of feeding from sawfly larvae or caterpillars of some type.

Comments from LEO Editors:

In June, Michael Opheim submitted an observation of extensive defoliation around Seldovia. Jessie Moan, an entomologist with the US Forest Service, wrote that they are seeing quite a bit of defoliation by external feeders throughout Southcentral. Based on this observation, it appears that damage extends up to Gakona as well.

The defoliator at fault depends to some degree on the species of plant, but there are numerous caterpillar species, and at least three species of sawfly, that may be responsible. More information on specific defoliators in Alaska can be found in the US Forest Service Insects and Diseases of Alaskan Forests booklet. The entry for birch aphids does note that they can be abundant in Southcentral and Interior Alaska, causing leaf-curling, browning, and some die back of aspen and spruce trees.

The US Forest Service updates a map of forest health ground surveys in Alaska. Crews are still working to collect information on forest health this year, but is a resource to look back on to see the impact of defoliators during 2020. Erica Lujan