Leaf miners are insect larvae that live and feed inside the leaf tissue of certain plants and cause damage to those plants. Leaf miners are difficult to control because they feed in between the leaf surfaces so they are protected from spray insecticides. They selectively feed on only the layers that have the least cellulose. The insect can be very harmful to crops like tomatoes, beans, peas and cucumbers, as well as water melon and squash. The blister like spots appear on the leaves where the small maggot like insect has eaten the plant tissue. This insect will overwinter in green houses or indoors. Leaf Miners can be controlled by using two methods, either by ground application of an insecticide or by foliar spray. Both should be done with a systemic insecticide. This will allow the insecticide to contact the larvae. Use Fertilome Tree & Shrub Systemic Drench to control these pests.