Mysterious Holes in Leaves

Observation by Darlene Crawford with Michael Opheim:

This is not just affecting one plant but multiple plants: willows, alders, rose bushes, and salmonberry bushes. Leaves are getting holes eaten in them across these different plants. It would be interesting to know if anyone else is seeing this and if this is one bug or multiple types of bugs just being extra hungry this year.

Jessie Moan, formerly with the UAF Cooperative Extension, writes:

It would be great to have pictures of the insects to make a more confirmed ID but here's a few things I can offer:

I think what is impacting these plants are different things. In the case of the rose, I would suspect some kind of caterpillar or sawfly larva but can't be sure without a picture of the specimen. Many of these types of pests feed from the underneath side of the leaves so there may be better luck in looking for the offending insect by flipping the leaves over.

For the alder, the case is similar. There are many caterpillars and sawfly larvae that feed on the leaves and could cause the damage seen here. There's a nice compilation of our alder defoliating pests here. Again, I would check the underneath sides of the leaves to try to find what is causing the damage.

As for the willow, it's a little less clear based on the photo. There's a couple of sawflies that will feed on willow and we are certainly seeing a lot of aphid feeding on willow. There can be some cross-over between willow and alder pests so it's possible what is impacting the one is also impacting the other but it could also be different things.

We are, generally, seeing a decent amount of defoliation by external feeders throughout southcentral and have seen some caterpillar outbreaks on the Kenai (most notably around Sterling). We have collected some caterpillars and are attempting to rear them to adults to obtain an accurate ID at this point, but I don't know much more than that.

Comments from LEO Editors:

There are three species of alder-feeding sawflies in Alaska: the alder woolly sawfly (Eriocampa ovata), the striped alder sawfly (Hemichroa crocea), and the European green alder sawfly (Monsoma pulveratum). The striped alder sawfly is native to Alaska, while the green alder and alder woolly sawflies are considered invasive or non-native. These three sawfly species emerge between mid May and mid June, and can cause extensive damage to alder leaves. More information on sawfly species of Alaska can be found here.

Kenai Peninsula communities are experiencing an abundance of battered sallow moth caterpillars (Sunira verberata), which have stripped a significant amount of foliage around Skilak Lake. The largest outbreak of battered sallow moth caterpillars occurred between 2003-2006 on the Alaska Peninsula, which may be linked to higher than normal temperatures.