Q Do trees get viruses?

— Molly Torinus

A Brian Hudelson, director of the Plant Disease Diagnostics Clinic at University of Wisconsin-Madison:

Definitely trees can get viruses.

There's a wide range of different plant viruses that infect not only trees but other types of plants as well: vegetables, fruits, herbaceous ornamentals. We see viruses on pretty much any type of plant.

But actually, the most important types of organisms that cause disease in plants are fungi.

One common fungus during the spring is cedar apple rust. This appears in mid-May to mid-June and forms huge, orange gelatinous masses on junipers, particularly red cedar. It’s very visual and very pretty.

Fungi are much more complex than viruses. They form a variety of different structures that are often visible to the naked eye.

In contrast, viruses are quite simple. They’re basically just a piece of genetic material encapsulated in a protein coat.

If you put a virus on an inert surface like a tabletop, it won’t do anything; it just sits there. The only way it’s able to make more virus particles is if it infects its host, such as a plant.

There are different ways that viruses can get into plants. Sometimes it’s just by touch. You can have a virus on your fingers and handle plants, and they will get infected. Some viruses are transmitted by insects, like ants.

When plants get a virus, they tend to be smaller and get funky growth distortions, weird discolorations and ring spots on their leaves.

And typically, once they’re infected, they’re infected permanently. Viruses just don’t go away.

Blue Sky Science is a collaboration of the Wisconsin State Journal and the Morgridge Institute for Research.