I have many plants in pots at my windows, and only my irises are affected (I have other parasites on other plants, but I usually don't really care as long as the plants are OK, as I am for bio-diversity, I let wild things like grass develop too).
They don't seem to be moving, but it's spreading on the plant. There is no sign of the leaves being eaten and the plants seem to be allright, but it's spreading quite fast and I fear the iris would suffer if it covers all the plant).
What is it? Should I get rid of it and if yes, how?
If needed, I live in France.