The maggots of this fly form communal mines in the leaves. Damaged areas at first appear as large, pale green blotches which soon dry up and become brown and papery. This gives the foliage the appearance of having been scorched. Parsnips, celeriac, parsley, lovage and related wild flowers are similarly damaged by this insect.
There are at least two generations during the year and mining occurs between early May and the autumn. The first generation is generally less numerous than the second, but it can cause a serious check to growth. This may result in small celery plants with a bitter taste. When the grubs have finished feeding, some pupate in the mines while others pupate in the soil.