Leaf Miners
Leaf Miners  Leaf miners are those insects that consume leaves and needles from within the foliage of the host plant. Those found attacking deciduous plants are known as "leaf miners" while those attacking conifers are "needle miners". Here, they will be collectively referred to as leaf miners. Leaf miners are found in many different insect orders, such as, lepidoptera (moths and butterflies), hymenoptera (leaf mining sawflies), coleoptera (the beetles), and diptera (the true flies). All of these are leaf miners while in the immature, or larval, stage of their life cycle. Depending on the species involved, some will pupate within the mined foliage while others emerge first and then pupate. Susceptible Plants- Tomato, pepper, spinach, squash and pumpkin., oaks, holly, chrysanthemum. Life Cycle- Female leafminers deposit eggs within leaf tissue. Larvae hatch from eggs in a few days and begin to feed on internal leaf tissues. Mature larvae emerge from inside the leaf and drop to the soil where they pupate in soil crevices, or in rare cases, they may pupate on the leaf. The timespan from egg to adult is less and three weeks under optimum conditions, so many generations occur annually. Symptoms- First symptoms are a white spotting of leaves caused by feeding of adult females. Narrow white tunnels appear between the upper and lower leaf surface. Then later widen meander toward the leaf midrib. After approximately 2 to 3 weeks, small dark bumps can be seen on the lower leaf surface. The primary damage caused by the leaf miner is the mining of the leaf by the larvae. When infestations are severe, the plant's photosynthetic capacity is reduced and there is a reduction in crop yield.  Prevention and Control- of leaf miners, in general, is usually best achieved during the part of the life cycle when the insect is not within the host plant foliage. Feeding within foliage offers some protection from predators and parasites by being unseen. However, there are those beneficial insects that specialize in being parasites of leaf mining insects. Many of these parasites being from the hymenoptera (wasps). Leaf miners may feed on the spongy mesophyll, palisade parenchyma cells and perhaps all but the upper and lower epidermis. Mines may be in the form of a blotch or may be more winding or serpentine. When many leaf miners are found within one leaf, mines may then coalesce into one large blotch-type mine. Organic/Biological Control- Leaf miners are controlled by Leafminer Parasitoid Diglyphus isaea ., Minute Pirate Bug Orius insidiosus 500 Insecticidal Control- Organic JMS Stylet is excellent as an insecticide and for virus control! It will control mites, whitefly and leafminer, as well as aphid-transmitted virus diseases. This year-round spray oil is OMRI listed and EPA registered; it can be used in greenhouses, on field crops, or on fruit trees.
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