Leafminer adults are small black and yellow
flies. Larvae are yellowish maggots that feed beneath the
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 that seedlings, although it may make spinach or chard
unsightly. In warm weather, leafminers may be more active.
The life cycle is only 2 weeks long. Eggs are inserted
into leaves and larvae feed between leaf surfaces, creating
a "mine." At high population levels, entire leaves
may be covered with mines. Mature larvae leave the mines,
dropping to the ground to pupate. There can be five to
ten generations per year. Development continues all year,
the population moving from one host to another as new host
plants become available each season.
Leafminers rarely require treatment in gardens. Small
seedlings can be protected by protective cloth. On plants
such as cole crops, 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.
damage to tomato leaf