Allium Leaf Miner
Risk near you, next 48h
See whether your local forecast favours this disease right now.
When it strikes
Treat, then re-check in 5–7 days
Pick off the worst material, apply the organic option below, and look again after five to seven days. If the spread continued, escalate rather than repeating the same treatment.
Carried by insects
An insect moves it plant to plant, so controlling the carrier matters as much as treating the symptom. Check for the vector before assuming the plants infected each other directly.
Safe to compost
No pathogen carries over on this material, so it can go on an ordinary heap with the rest of the garden waste.
When and where to look
Scout the planting while temperatures hold between 8°C and 25°C.
Rule these out first
Same category, and at least one host crop in common — so they are genuinely confusable in the same part of the garden.
The signs that lead here
Full problem lists for these crops
About
Allium leaf miner (Phytomyza gymnostoma) spread across Europe from the 1990s and is now a major pest of leeks, onions, garlic and chives. There are two flight periods — roughly March to April and October to November — and almost all the damage is done in those two windows.
Symptoms
A line of small white dots down the leaf, made by adults feeding, is the first sign. Larvae then tunnel down into the stem and bulb, where they pupate as brown rice-grain-shaped puparia. The plant distorts, rots and is usually unusable.
Organic Treatment
Cover the crop with fine insect mesh during both flight periods — nothing else works reliably. Remove and destroy infested plants with their puparia rather than composting them.
Chemical Treatment
No garden insecticide reaches larvae inside the stem, and adults are present only briefly. Exclusion is the entire strategy.
Prevention
Time planting so that a crop is not standing uncovered during the two flight periods where possible, rotate away from alliums, and check every plant before storing — a single infested leek passes puparia into the store.
Crops at risk
Related problems
Allium Leaf Miner risk by location
Each location has a month-by-month profile computed from the weather archive: how many hours a year actually meet this disease’s thresholds.