Divisi
Leaf miners
Liriomyza spp. · Insect
Photo: Flowersabc · CC BY-SA 2.0
Leaf miners (Liriomyza flies) are tiny black-and-yellow flies whose pale, legless maggots tunnel inside the leaves of tomato, beans, onion and cucumber, leaving winding white trails. The adult flies also punch little white holes in the leaf to feed and lay their eggs. Heavy mining dries and disfigures the leaves and starves the plant of light — and because the maggots hide inside the leaf where surface sprays cannot reach, the biggest outbreaks are usually triggered by broad poisons that kill off the tiny wasps that normally keep miners in check.
Retired electrician · CC0 
N3v3rl4nd · Public domain
Why it matters
Leaf miners can cost you up to a third of your crop (30%) on tomato, beans, onion and cucumber — and they hit hardest on young seedlings and fresh transplants, which have too few leaves to spare any. The damage is done by tiny maggots tunnelling inside the leaf, where an ordinary spray on the surface can never reach them. Worst of all, a bad outbreak is usually something you bring on yourself: broad poisons meant for other pests kill the tiny wasps that keep miners down, and once that free, natural control is broken the flies breed back fast and become very hard to stop. So the whole game is protecting those helper wasps and catching mines early, while your plants are still young.
When to act
several fresh serpentine mines per leaf on a majority of plants, especially on seedlings and young transplants
This guidance is general, compiled from published agronomic references including FAO and CABI. Thresholds and timing shift with your crop, your variety and the season.
In much of the region a spray is simply called mushonga — medicine. But a chemical group you cannot name is one you cannot rotate, and a product you did not write down has no pre-harvest interval you can observe. Mushonga, and other farming words →
The full leaf miners field guide
- Identify it
- Scout for it
- Control it
14 field-guide sections in the app
The full guide to leaf miners — every symptom to check, how and when to walk your field looking for it, and the controls that actually work, ranked. Built into your crop plan, so you are told to look before it costs you a harvest.
Crops it affects
Frequently asked questions
How do I identify leaf miners?
The damage (first and clearest sign): pale, winding tunnels in the leaf — like a snake's trail or a scribble of white thread across the leaf. Each mine starts thin and grows wider as it goes, and if you look closely a fine dark line runs down the middle (that dark line is the maggot's droppings, called frass). Badly mined leaves turn papery, dry from the edges, and drop early.
When should I take action against leaf miners?
several fresh serpentine mines per leaf on a majority of plants, especially on seedlings and young transplants
How do I control leaf miners?
Prevent it — start clean and stay clean: plant only mine-free seedlings (check them and throw out any with tunnels), pick off and bury or burn the worst-mined leaves as you find them, and after harvest plough or dig in all crop residues so the pupae (the resting stage the maggot turns into before it becomes a fly) hidden in old leaves can't carry over to your next crop. Where you can, rotate to an unrelated crop so miners don't build up in the same spot season after season.
Which crops does leaf miners affect?
Among the crops covered here: Cabbage, Cucumber, Onion, Tomato.
Catch it before it costs you a harvest
Divisi builds scouting into your crop plan — it tells you when to walk your field, what to look for at that stage, and what to do when you find it. Free for farmers, works offline.
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