When I was young, I used to think that leaves just naturally got spotty and brown as they aged. But after taking plant pathology, I learned those spots you seen on leaves are almost always fungi or insects infesting plants, and careful examination with a hand lens can reveal a whole new little world to you. As we walked through the woods last week, I saw many leaves with yellowing spots on top. I turned them over, and lo, underneath were creamsicle-orange piles of rust spores.
Rusts are one of the oldest known plant pathogens, and the Romans even had a god –Robigus — dedicated to staving off the stuff (and that included the rust of metal — not having microscopes, Romans considered them one in the same). Rusts are fungi that go through incredible reproductive gymnastics, producing up to five seqeuential spore types in five different reproductive structures and jumping among two or three different hosts per life cycle. I think the rusts are abundant this year because we had such a wet June in Colorado, but that is just a guess.
Heavy infestations hurt plants, but in the woods they are very pretty to see if you turn over leaves to see the eponymous rusty-orange urediospores underneath. Mycologists have long, difficult-to-pronounce names for each rust spore type and spore-making body (naturally), but we’ll save those for another post. Just like our jelly fungi and zygomated mushroom, rusts are basidiomycetes, one of the four major groups of fungi. The others, for reference, are chytridiomycetes, zygomycetes (as we saw last time), and ascomycetes.
Ascomycetes are fungi that make their spores inside sacks called asci (yes, pronounced ass-eye (singular ascus: ask-us). My plant path grad school department once had a soccer team named after asci that grow without an enclosing structure: “The Naked Asci”), and we found several of these on wet wood too. Many, but by no means all, come in cup form. Eyelash cups (Scutellinia scutellata), in particular, peppered many waterlogged branches with their lashed but lidless eyes.
A body double for our Molly eye-winkers -- I forgot to get a picture. Image courtesy Dan Molter, Creative Commons 3.0 Attribution-ShareAlike 3.0 license. Click image for link.
Next time: Slime molds. I promise. Also snails. Cute snails. You know you can’t resist.
