Blog‎ > ‎

June 2019 Natural Mystery Answered

posted Jul 5, 2019, 2:07 PM by Jonathan Poppele   [ updated Jul 6, 2019, 11:50 AM ]
Our June Natural Mystery was really a three-part question—identify the plant, identify the bulge at the end of it, and explain how it ended up on the ground looking the way it did. It is clear that we have some experienced foresters in the group, in addition to a great many excellent trackers. Congratulations to Rachael Olesiak identified every organism involved here to the species. Honorable mentions go to Deb Sweeney, who correctly identified the plant and the cause of the bulge on the twig, and to Jim Carretta who identified the animal involved and it's behavior.

Let's begin with Rachael Olesiak's succinct answer to the question:

A red squirrel chewed on the gall of a jack pine from pine-pine gall rust.

Deb Sweeney offers some additional details about the plant and the gall:

Step one is identifying the twig. It's a pine because it has needles in bundles of two. Jack pine because the needles are under 1" and are widely spread. Then let's look at the blob. It looks weird and it is on a plant, therefore it is a gall (my personal rule of thumb). Galls are specific to plants. Googling "jack pine gall" we get Pine-Pine Gall Rust which has an oblong shape and has a similar appearance.


Rachael and Deb are exactly correct. This is a Jack Pine twig with a gall on the tip caused by the oddly named Pine-Pine Gall Rust. Pine-Pine Gall Rust, also known as Western Gall Rust, is a disease caused by the fungus Endocronartium harknessii which grows in the vascular cambium of it's host. The fungus uses pine trees as hosts for both parts of its life cycle. Hence the “Pine-Pine.” A related disease, Pine-Oak Gall Rust, is caused by a fungus that requires pine trees for one part of its life cycle and oaks for another.

Jim Carretta recognized the bulb as some kind of gall, and correctly added:

The branch was one among many clipped by a squirrel while high in the tree. The photo shows some teeth marks on the gall / bulb.

Thanks again to everyone who submitted answers, and to Kirsten Welge for providing this mystery for us. I learned a lot researching this and reading the responses and hope you all did as well.



Support the Newsletter on Patreon

If you enjoy these natural mysteries, please consider supporting the Minnesota Wildlife Tracking Project newsletter on Patreon.