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

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. Should not be confused with Tuta absoluta (Tomato Leafminer) whose mines on leaves are wider and white or transparent.

Trigger

Symptoms are caused 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. Leaf miner flies are attracted to the color yellow.

Biological Control

Glue traps can be used as a direct method of pest suppression. Spray neem oil products (Azadirachtin) against larvae onto leaves in the early morning or late evening. For example, spray Neem oil (15000 ppm) at a rate of 5ml/l. Make sure to have good leaf coverage. Neem slightly enters the leaves and reaches some of the larvae inside the tunnel. Foliar applications of the entomophagous nematode, Steinernema carpocapsae, can reduce the leaf miner population. Other biological controls of leaf miners include parasitoids (e.g.Chrysonotomyia punctiventris and Ganaspidium hunteri) and nematodes (e.g. Steinernema carpocapsae).

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, Chlorantraniliprole, Acetamiprid, Spinetoram or Spinosad can be used in a rotation to avoid the development of resistance.

Preventive Measures

  • Use crop varieties with curled leaves as they are less susceptible to leaf miner damage and may provide suitable alternatives where leaf miner damage is expected.
  • Check transplants for leaf miners or mines before planting and destroy any plants that are infested (leaf miners reach damaging levels earlier when infestations begin on transplants).
  • Monitor weekly at all growth stages of crop.
  • Look for tiny thread-like tunnels (mines) on the upper leaf sides.
  • Look for larvae inside tunnels or on the upper side of leaves.
  • Use glue traps or yellow sticky traps to see whether Leaf miners are present.
  • At 8 to 12 infected plants per 100 plants, consider direct control action.
  • Handpick heavily infested leaves with many leaf miner tunnels, and destroy them by crushing or burying them, or feeding them to cattle if palatable.
  • It is important to destroy and bury the remains of broadleaf weeds and senescent crops as they can harbor reproductive leaf miner flies.
  • Where a series of tomato crops are planted in the same area, you can reduce early infestations in a new crop by removing old plantings immediately after the last harvest.