Leafminers tunnel within leaves, giving foliage an unattractive appearance. In addition to a cosmetic problem, leafminers can also damage beets, chard, and columbine.
Adults are flies that are black, or black and yellow, and are 1/10 of an inch (2.5 mm) long. You will rarely see them. Their larvae are pale green, stubby, and translucent maggots that are found in the tunnels in the leaves. Eggs are white and cylindrical.
Adults emerge from overwintering cocoons in early spring and lay their eggs side by side in clusters on the undersides of leaves. The larvae mine leaves for 1 to 3 weeks, then pupate for 2 to 4 weeks inside the leaf or they can drop to the soil to pupate. There are normally 2 to 3 generations per year; more in greenhouses.
PLANTS MOST AFFECTED
Bean, beet, cabbage, chard, lettuce, pepper, tomato, and many other vegetables. They also attack many ornamentals, especially chrysanthemum and nasturtium.
Larvae tunnel through the leaf tissue, making hollowed-out, curved, or winding mines. Larval damage can kill seedling plants by removing chlorophyll and reducing the plants photosynthetic capacity. Mines and feeding punctures also produce an entrance for pathogenic organisms. Excessive leaf mining in older plants can cause leaves to dry, resulting in sunburning of fruit and reduction in yield and quality. In severe infestations, leafmining may cause plant death.
1. Cover seedlings with Floating Row Covers to keep adult flies from laying eggs on leaves. Keep covers on all season if the pests are numerous.
2. Remove any nearby dock or lamb’s-quarters because they are natural hosts for beet leafminers.
1. Handpick and destroy any mined leaves.
2. Remove any egg clusters as soon as they are visible.
3. Spray Neem Oil.