Leaf Miners
Risk near you, next 48h
See whether your local forecast favours this disease right now.
When it strikes
Watch it before you act
At this level the damage rarely costs the crop. Note the date, check twice a week, and act only if it reaches new growth or the weather turns favourable for it.
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 12°C and 30°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
Leaf miners are the larvae of various flies, moths and sawflies that live and feed between the two surfaces of a leaf. On beet, chard, spinach and many ornamentals the damage looks alarming but is largely cosmetic — the plant keeps growing around the mines.
Symptoms
Pale winding tunnels or irregular blotches within the leaf, with the surfaces intact above and below. Hold the leaf to the light and the larva is visible as a dark speck at the end of its tunnel.
Organic Treatment
Pick off and destroy mined leaves as they appear — this removes the larvae before they pupate and is enough to keep numbers down on a garden scale. Squash the larva inside the mine between finger and thumb if you would rather keep the leaf.
Chemical Treatment
Contact sprays cannot reach a larva inside the leaf, so they are close to useless. Systemic products work but are disproportionate for a mostly cosmetic problem.
Prevention
Cover susceptible crops such as beetroot and chard with fleece in spring, clear fallen leaves where pupae overwinter, and leave the parasitic wasps that attack miners undisturbed by avoiding broad-spectrum sprays.
Crops at risk
Related problems
Leaf Miners 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.