When harvesting some of my lovage I noticed that some foilage has dried out or has large yellow spots. In one of the leave I saw an inhabitant - see below. This maggot was inside the leave: on both side there was still a layer.
What is this maggot and how can I prevent its parents to infiltrate my the leaves? Preferably in an organic way.
The maggot is located in the yellow bubble in the center of the leave on the right side.
After I ejected the maggot.