Capsicum & Chili
Black & Green Gram
Pigeonpea & Red Gram
Chickpea & Gram
Irregular or serpentine pale grey lines appear on both sides of the leaf blades as the larvae feed. These burrows are usually limited by the leaf veins and contain black fecal material visible as slim trace inside the tunnels. Entire leaves may be covered with mines. Damaged leaves may drop prematurely (defoliation). Defoliation can reduce yield and fruit size and expose fruit to sunburn.
Symptoms are cause by several flies belonging to the family of the Agromyzidae, with several thousand species worldwide. In spring, females puncture leaf tissues and lay their eggs, usually along the margins. The larvae feed between the upper and the lower leaf surface. They produce large white meandering tunnels with a trail of black fecal material (frass) left behind as they feed. Once they have reached maturity, larvae open a hole on the underside of the leaf and fall to the ground, where they pupate. Plant debris near the host are alternative pupating places. Leafminer flies are attracted to the color yellow.
Minor infestation just leads to cosmetic damage and does not affect productivity. Parasitic wasps that kill leaf-miner larvae in the mine are commercially available. Ladybirds are also predators of the leaf miner fly. Neem oil, Neem Seed Kernal Extract (NSKE 5%), Neem oil (15000 ppm) @ 5ml/l or Spinosad deter adults from feeding and reduce egg laying, thus limiting damage. These products have a low impact on natural enemies and pollinators.
Always consider an integrated approach with preventive measures together with biological treatments if available. Broad-spectrum insecticides of the organophosphates, carbamates and pyrethroids families prevent adults from laying eggs, but they do not kill the larvae. Moreover, they can lead to the decrease of natural enemies and the development of resistance in the fly, which in some cases can actually result in an increase in their numbers. Products such as abamectin, bifenthrin, methoxyfenozide, chlorantraniliprole or spinetoram can be used in a rotation to avoid development of resistance.