Article abbreviated from Gene McAvoy, 5-county UF/IFAS Veggie Agent
Identification
The adults are small yellow and black flies about the size of gnats. The female punctures or stipples the leaves with her ovipositor to lay eggs in the leaf tissue or to feed on sap.
Leafminer damage is easily recognized by the irregular serpentine mines in leaves. The maggots feed on tissue between upper and lower leaf surfaces, leaving a winding trail or pattern through the leaf.
Survival And Spread
To determine whether leafminer larvae are dead or alive, leaflets can be held up to the sun and examined with a hand lens. Living larvae are a pale yellow and flush with the end of the mine. The back and forth feeding movements are readily visible, although movement may cease when larvae are disturbed or molting. Dead larvae do not show movement and are usually discolored and removed from the ends of mines.
Management Gene's recommendations are for commercial growers with access to products that homeowners don't have.
Karen's inserted note here: liquid soap (NOT Dawn) and horticultural oil. Read the label for the plants you are spraying it on. Liquid soap is 1/2 to 1 Tablespoon per gallon. Remember to spray the under side of the leaves. Spray as soon as the plant is dry and before the bees start visiting it.
Field sanitation is another important control tactic. Weeds and abandoned crops can serve as reservoirs for this pest.
Thanks Gene for such great articles!
