Leaf miner
Its maggot tunnels between the leaf surfaces, leaving winding whitish trails — mostly cosmetic, but damaging on seedlings and leafy crops.
- Pest type
- Leaf-mining maggot
- Attacks
- Inside the leaf
- Worst in
- Seedlings; leafy crops
- Main risk
- Dried leaves; spray-induced flare
Overview
Leaf miners are the tiny maggots of small flies (and, in groundnut, a small moth) that feed inside the leaf, tunnelling between the upper and lower surfaces and eating the green tissue as they go. The result is the tell-tale winding, whitish or silvery "serpentine" trail that widens as the maggot grows — the leaf tissue is hollowed out while the surfaces stay intact.
On an established, vigorous crop, moderate mining is largely cosmetic and natural enemies (many parasitic wasps attack leaf miners) keep it in check. It matters most on seedlings, on leafy vegetables where the leaf is the product, and when heavy mining dries large parts of the canopy. In groundnut, the leaf miner also webs and folds leaflets. Over-spraying is a common mistake — broad-spectrum insecticides kill the parasitoids and make leaf miner worse.
How to identify it
- Winding, whitish or silvery "serpentine" trails inside the leaf that widen along their length, with the leaf surfaces intact.
- Held to the light, the tunnel shows the mined-out track and sometimes the tiny maggot at the end.
- Heavily mined leaves that dry out in patches and, on seedlings, stunt the plant.
- In groundnut, mined leaflets that are also webbed and folded together.
The damage it does
- Mined, hollowed leaf tissue that reduces photosynthesis when infestation is heavy.
- Real damage on seedlings and on leafy vegetables where the mined leaf is the marketable product.
- Dried, papery patches and premature leaf fall in a severe attack.
- Resurgence after broad-spectrum sprays that kill the parasitic wasps controlling the miner.
When to act
- Judge by severity and stage — light mining on a vigorous crop rarely needs action, while heavy mining on seedlings or leafy crops does.
- Yellow sticky traps catch the adult flies and help monitor build-up.
- Avoid reflexive spraying; check whether parasitic wasps are already at work before treating.
Organic & cultural control
- Conserve the parasitic wasps that attack leaf miners — they usually keep it below damaging levels; avoid broad-spectrum sprays that kill them.
- Remove and destroy heavily mined leaves early to take out the maggots inside.
- Spray neem (NSKE 5%), which deters egg-laying and checks young maggots, and use yellow sticky traps for the adult flies.
- Keep the crop vigorous and weed-free, and destroy residues after harvest.
Chemical control
- Reserve insecticides for heavy infestations on seedlings or leafy crops — CIB&RC-registered options for the crop, used selectively so parasitoids are spared.
- Prefer selective products and correct timing over repeated broad-spectrum sprays, which trigger leaf-miner resurgence.
- Observe the pre-harvest interval strictly on leafy vegetables and frequently-picked crops.
- Confirm the current recommendation and dose for your crop and zone with your local KVK.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Frequently asked questions
My leaves have winding white lines inside them. What causes it?
Those winding, whitish "serpentine" trails inside the leaf are leaf miner damage — a tiny maggot tunnels between the upper and lower leaf surfaces, eating the green tissue and leaving the trail, which widens as it grows. Hold the leaf to the light and you can often see the maggot at the end of the tunnel.
Do I need to spray for leaf miner?
Often not. On a vigorous, established crop, moderate mining is mostly cosmetic and parasitic wasps usually keep it in check. Spraying matters mainly on seedlings and leafy vegetables, or when mining is heavy. Reaching for a broad-spectrum insecticide can backfire by killing the parasitoids and making leaf miner worse.
Why did spraying make leaf miner worse?
Because broad-spectrum insecticides kill the many parasitic wasps that naturally control leaf miner, letting it resurge worse than before. Conserve the parasitoids, use neem and yellow sticky traps, remove heavily mined leaves, and reserve a selective registered insecticide for genuinely heavy infestations on vulnerable crops.
Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.