I’ve probably ignored the yellowing leaves of various willowherb species when I’ve seen them previously, thinking they were just drying out or perhaps diseased, but this time I turned a leaf over and discovered a new fungus (and lots of tiny orange grubs – likely fungus gnat larvae – feasting on that fungus).

This is Willowherb rust (Puccinia pulverulenta) (luckily, most rust species are host specific so are easy to identify if you know what the host plant it). The tiny orange rings, which, with their white fringing look a little like miniature flowers, are aecia – it’s from these that the rust releases some of its spores. Later in their complicated life cycle, the rust also produces the brown uredinia that can be seen in the photo on the right below. (Rust fungi have five different spore states – if you want to delve in to that life cycle, Science Direct has a good explanatory, though very technical article on its website.)