Leafminers may be more active during warm weather, but they are in the garden year-round. They move from plant to plant with each season. The most obvious evidence of leafminers is the twisting trails (or mines) the larvae leave as they feed beneath the leaf surface. Damage will not be serious on most plants older than seedlings, although it may make spinach or chard unsightly.
Leafminers rarely require treatment in gardens. Small seedlings can be protected by
row covers. On plants such as cole crops (broccoli, cabbage, brussels sprouts), lettuce, and spinach, clip off and remove older infested leaves. Leafminers are often kept under good control by
natural parasites. Insecticides are not very effective for leafminer control.
Read more about
vegetable leafminers.