Leaf miner in margarita leaves

[Marb67]

Well, the curse of leaf miner continues with yet another strain in my Margarita leaves. Every year this prolific plant is spoilt by the massive infection in the leaves. Even though I have taken this small cutting, potted in NEW soil and kept indoors it's already showing signs. I have absolutely no idea how and why but it's awful. A lot of my pants have it in one form or another

[Jungle Jane]

Leaf miner adults are flies I think,it’s easy for the fly to go round the whole garden egg laying,I just remove the trail making black dot/leaf miner,cut part the leaf off or squash with a fingernail if you can see it,put the leaf bits in the rubbish bin away from compost heap so they can’t develop into the pest.