Soybean
Leaf Miner Flies
Agromyzidae
Insect
5 mins to read
In a Nutshell
- Tunnel-like grey lines on the leaves.
- Tunnels delimited by leaf veins.
- Leaves may drop prematurely.
Soybean
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.
Recommendations
Organic Control
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 5 ml/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.
What caused it?
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 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.
Preventive Measures
- Favor crop varieties with curled leaves.
- Check transplants for leaf miners or mines before planting.
- Destroy any transplants that are infested.
- Monitor weekly and at all growth stages of the crop.
- Look for tiny tunnels and larvae inside the tunnels on the upper leaf sides.
- Use glue traps or yellow sticky traps to detect leaf miners.
- At 8 to 12 infected plants per 100 plants, consider direct control action.
- Handpick heavily-infested leaves, and destroy them by crushing or burying them, or feeding them to cattle if palatable.
- Destroy and bury the remains of weeds and dying crops.
- Remove crop debris immediately afert harvest is finished, especially for tomato crop.
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