Arum Rust Puccinia sessilis
Wild Arum [i]Arum maculatum[/i] is abundant in woodlands and similar habits at this time of the year. Some of them have yellowish discs on the upper surface of leaves.
In the corresponding positions on the undersides of the leaves are groups (about 7-8mm across) of these aecia, the spore bearing structures of the rust.
Eventually, where there was a yellow spot there is black spot then a hole.
These images were taken on my EM-1 (1) with the Olympus 4/3 50mm f2 macro, some with the x2TC behind it, or with the Laowa 25, x2.5 to x5 at x2.5and f11. I used natural light for the low power and twin flash for the others. All hand-held.