Leaf Miner Flies

  • Symptoms

  • Trigger

  • Biological Control

  • Chemical Control

  • Preventive Measures

Leaf Miner Flies

Agromyzidae

Insect


In a Nutshell

  • Tunnel like grey lines on the leaves.
  • Tunnel delimited by leaf veins.
  • Leaves may drop prematurely.

Hosts:

Apple

Bean

Capsicum & Chili

Eggplant

Pea

Cucumber

Pumpkin

Zucchini

Tomato

Cabbage

Potato

Black & Green Gram

Pigeonpea & Red Gram

Chickpea & Gram

Cotton

Soybean

Other

Onion

Okra

Peanut

Mango

Papaya

Ornamental

Symptoms

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.

Trigger

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.

Biological Control

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.

Chemical Control

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.

Preventive Measures

  • Plant seedlings free of eggs of leafminer flies.
  • Choose varieties with curled leaves that are less susceptible to the pest.
  • Avoid planting alternative hosts next to infested fields.
  • Monitor fields for signs of the insect on leaves.
  • Use yellow sticky traps or yellow basins filled with water to catch the flies.
  • Handpick and destroy mined leaves or heavily-infested plants.
  • Plant hedge rows of flowering plants to prevent migration of the fly.
  • Remove weeds and volunteer plants in and around the fields.
  • Apply mulch around plants to prevent the flies from breeding in the soil.
  • Do not use broad-spectrum insecticide that could affect natural enemies.
  • Plow deep to expose the miners to natural enemies.
  • Alternatively, burn infected plant debris after harvest.
  • Rotate crops with non-susceptible crops.