Think your life is complicated? Be glad you’re not a rust fungus. If you were a rust fungus, you’d have one of the more complicated life cycles on Earth, because you’d need to find and live on two different (but specific) plants to survive and reproduce. To make life even more complicated, you’d have millions of babies (spores), and sometimes you wouldn’t even get to have sex before making your babies. Instead, they would just happen, spontaneously, when the time was right. Like, maybe one day you’d be sitting outside and it gets warm and rainy and all of a sudden you’re swelling and popping out spores. Crazy, right? But to top it all off, you might look like an alien.
Take, for instance, my personal favorite rust fungus, the cedar-apple rust, which I fondly call “The Orange Alien Fungus,” because that’s what I aptly called it before I knew its real name. The cedar-apple fungus (Gymnosporangium juniperi-virginianae) has two hosts: cedars/junipers and apples/crabapples. In late spring, when weather gets warmer and wetter, hard, brown balls called galls that hang out on cedars all winter begin to become more gelatinous (gross) and grow orange alien tentacles (see picture). These tentacles release spores that, if they land on apple trees in moist conditions, can enter their next complicated life stage. These tiny spores released by the tentacles can travel 2-3 miles on the wind, so even if you don’t see any apple trees around, your cedar-apple alien could be making babies 2 miles away or more. Once on the apple tree, the spores will grow, and you will begin to see rust-colored spots on the leaves or apples of the tree. If you were to look at the spots under a microscope (I know you wouldn’t, but work with me here), you would see cup-shaped structures full of new spores (no sex, sadly). These spores stick to insects that transport them to new cedars, where they grow into the hard, brown balls that started our story. So, to summarize the complicated life of the cedar-apple rust, you would start out as a spore carried by an insect, grow into a hard, brown ball on the branch of a cedar tree, then grow orange disgusting tentacles, have sex and make baby spores, which would grow into spots on apple trees that make the kind of spore you originally came from.
Cedar-apple rust does not do much damage to cedar trees, unless you count being covered with disgusting orange alien balls as damage. However, cedar-apple rust can cause economic damage to apple crops. If you have to manage the disease, you can prune the galls off of cedar trees in the winter. Or, you can buy rust-resistant varieties of apple, which include the varieties called Redfree, Liberty, William’s Pride, and Freedom. Cedar-apple rust is just another example of just how complicated and weird being alive on Earth can be. I hope you’re enjoying your weird, complicated life as much as cedar-apple rusts must be.