Leafminer fly (Grafitti flies)

Introduction There are four leaf miner species which are common pests: the tomato leaf miner (Liriomyza bryoniae), the American serpentine leaf miner (Liriomyza trifolii), the pea leaf miner (Liriomyza huidobrensis) and Liriomyza strigata. Under natural conditions, the larvae of these species are well parasitized by several natural enemies. Problems with leaf miner have increased as a result of the use of broad-spectrum pesticides: natural enemies are killed and the leaf miners develop resistance to these insecticides.

Biology The leaf miner goes through six stages, namely egg, three larval stages, pupa and adult. The adult leaf miners are small, yellow and black coloured flies. The larvae form mines in the leaves of plants. Pupation takes place mostly in the soil. Damage symptoms Larvae cause mines. This can lead to cosmetic damage, leaves drying out or even early defoliation. The latter may affect the yield. Female adults cause feeding marks where they feed. This gives cosmetic damage to the plants. Indirect damage occurs when fungi or bacteria enter the feeding areas. Solution Stiky Traps Many insects are attracted to the color yellow. These insects can be captured by hanging cards around your plants. Captured adults will not lay any more eggs on your plants. Yellow Stiky traps provide a means of controlling the flying stages of most pest insects. Monitor plant leaves closely. At the first sign of tunneling, squeeze the leaf at the tunnel between two fingers to crush any larvae. Done soon enough, this killing larvae can allow plants to survive minor outbreaks. Pick off and destroy badly infested leaves in small gardens. The more healthy the plant, the less chance that leafminers will hurt it. Maintain plant health with organic fertilizers and proper watering to allow plants to outgrow and tolerate pest damage. Keep your soil alive by using compost and other soil amendments. Use floating row covers to prevent fly stage from laying eggs on leaves. The parasitic wasp Diglyphus isaea is a commercially available beneficial insect that will kill leafminer larva in the mine. The wasp is especially beneficial to indoor growers of ornamentals and vegetables. Use yellow sticky traps to catch egg laying adults. Cover soil under infested plants with plastic mulches to prevent larvae from reaching the ground and pupating. Organic neem oil will break the pests’ life-cycle by preventing larva from reaching maturity. Neem oil may also have repellent qualities and interfere with egg laying activities. Botanical insecticides can be used to knock down adult insects but have little effect on the protected larval stage feeding inside the leaf. Do not compost soil or plant material that may be infested.Mulch beds to help control population mulching also  helps retain soil moisture and helps new leaves grow to replace damaged leaves. for more info check this site http://www.planetnatural.com/pest-problem-solver/houseplant-pests/leafminer-control/