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I often see this type of leaf mine on black poplar (Populus nigra), but also on Populus nigra cv. Italica. I noticed it a few weeks ago, but all the leaf mines are already empty. Sometimes I only find the initial short, light green gallery, while the blotch part has already has detached (e.g. here: https://www.inaturalist.org/observations/311079069). In the attached photo you can still see the whole leaf mine (both parts). Do you think *Japanagromyza salicifolii* is the culprit? I’m uncertain, since I couldn’t find any records of this species from Central Europe.
Answer
Dear Sajti, thank you for your very interesting question. Under the bark of young poplar shoots there is a mine – the tissue has been eaten by the larva of a small moth. Several species can behave in a similar way, but in your case it is most likely the species Phyllocnistis extrematrix. Wishing you a nice day, best regards, M. Zúbrik