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Leafminers

A pale trail or blotch between leaf surfaces suggests a miner, but old mines can be empty. Match the host, live larva and injury to the part of the plant you need to protect.

Latest source check 15 October 2026Source-led field guide
Make an action plan

Match the organism, its setting and its signs. A photograph or a single symptom cannot confirm every species or cause.

Leaf mines attributed to Liriomyza commelinae
Photographed exampleLeaf mines attributed to Liriomyza commelinae.Liriomyza commelinae
Identification limits & photo credit

Shows pale winding mines and dark material within them. One leaf-miner example; mine shape alone cannot identify every miner or prove that larvae are still active. Host plant not named in the source.

Leaf mines attributed to Liriomyza commelinae. Photo: Even Dankowicz. CC BY 4.0. Original source · CC BY 4.0 & details

01 / IdentifyCheck the evidence ↗02 / RespondChoose the next step ↗03 / Follow throughKnow what to check ↗
In this guide
Your first decision

Remove a limited active source

Pick off a few occupied leaves while preserving enough foliage for growth. Do not strip an established plant just to remove old marks.

Sources for this section

UC Statewide IPM Program · University of Minnesota Extension · UC Statewide IPM Program

01 / Identify

Recognize the signs

Mines
Winding trails or expanding pale blotches within a leaf can contain a larva and dark waste. Damage is inside tissue rather than an open chewed hole.
Activity
Hold a leaf to the light and look for a live occupant. An empty mine will remain visible after the insect leaves.
Sources for this section

UC Statewide IPM Program

Differences that change the decision

A similar-looking organism can need a different response. Compare the evidence and what it changes.

Compare every column. On a narrow screen, scroll the table sideways.

TypeWhat to checkWhat changes
Serpentine vegetable leafminersLiriomyza fly larvae make narrow, winding mines on many vegetables.Small plants and crops harvested for leaves merit closer attention than a mature plant with limited mined foliage.
Spinach and beet leafminersPegomya larvae create broader blotches in spinach, chard, beets and related hosts.Protect the edible leaf crop early; a beet grown for its root can tolerate some leaf injury.
Woody-plant foliage minersMines on particular trees or shrubs can come from different flies, moths or other insects.Host identity and mine shape narrow the search. Do not apply vegetable advice to a tree without identifying the miner.
Sources for this section

UC Statewide IPM Program · University of Minnesota Extension

What else could it be?

Leaf spots, scorching or physical abrasion

These do not form a tunnel containing a larva or waste, although damaged tissue can later break apart.

Compare plant disease & stress

External caterpillars

Chewed holes, webbed leaves and exposed frass suggest feeding outside the leaf.

Compare caterpillars
Sources for this section

Virginia Cooperative Extension

Inspect the right places

  1. Check whether the mine is occupied

    Photograph the whole leaf, its underside and a backlit close-up; include the plant name and growth stage.

  2. Review last year's bed

    A cover can trap emerging miners beneath it if a susceptible crop or infested residue occupied the same soil previously.

Sources for this section

University of Minnesota Extension · Virginia Cooperative Extension

02 / Respond

Choose a proportionate response

For pesticides, the local product label determines the allowed pest, site, precautions and timing. Check safety and regional guidance.

  1. Remove a limited active source

    Pick off a few occupied leaves while preserving enough foliage for growth. Do not strip an established plant just to remove old marks.

  2. Exclude before infestation

    Appropriate insect mesh or row cover can protect susceptible vegetables, provided pests are not already underneath. Account for heat and any crop pollination needs.

  3. Keep natural control intact

    Many miners are parasitised. Broad insecticides can remove those enemies while leaving larvae protected inside leaves; seek host-specific advice for serious damage.

Turn these steps into your own checklist ↗
Sources for this section

UC Statewide IPM Program · University of Minnesota Extension · UC Statewide IPM Program

Avoid these mistakes

  • Do not treat every empty mine.
  • Do not assume a sticky adult trap controls larvae within leaves.
  • Do not expect a cover placed over an infested crop to remove insects already present.
Sources for this section

UC Statewide IPM Program · UC Statewide IPM Program

03 / Follow through

Check whether it is working

When to look again

Suggested practice: revisit the same leaves and inspect newly expanded leaves at least weekly, more often on vulnerable seedlings or a rapidly affected leaf crop.

Evidence of progress

Fewer new occupied mines and adequate healthy growth; old trails do not heal.

Record an observation ↗

Get help when…

  • Repeated crop loss or uncertain tree/shrub miner: local extension or plant clinic.
  • A new or unusual pest on imported plants: local plant-health authority before moving material.
Prepare for a professional inspection ↗
Sources for this section

University of Minnesota Extension

Prevent a return

  • Inspect transplants and remove infested crop debris according to local advice.
  • Rotate susceptible beds where practical and time protective covers before adult access.
Sources for this section

UC Statewide IPM Program · University of Minnesota Extension

Common questions

Are all mined leaves a reason to spray?

No. Plant age, live larvae, injury level and whether the leaf itself is harvested determine the useful response.

Why did leafminers appear under my net?

They may have entered before covering, through gaps, or emerged from infested material or soil already inside.

Sources for this section

University of Minnesota Extension

Check the evidence

Sources & scope

References retain their geography and dates. A source-check date is not a claim of independent specialist review.

  1. Vegetable Leafminers

    UC Statewide IPM Program. California, United States; biology may transfer, management timing and permitted products require local verification; source check, not expert review Checked 2026-10-15.

  2. Leafminers

    University of Minnesota Extension. Minnesota, United States; season dates and field thresholds are not universal; source check, not expert review Checked 2026-10-15.

  3. Biological Control and Natural Enemies of Invertebrates

    UC Statewide IPM Program. California, United States; biology may transfer, management timing and permitted products require local verification; source check, not expert review Checked 2026-10-15.

  4. Diagnosing Plant Problems

    Virginia Cooperative Extension. Virginia, United States; general diagnostic method; source date 2023-11 review; source check, not expert review Checked 2026-10-15.

Individual medical or veterinary diagnosis, structural assessment, uncertain species identification and local treatment permissions require the appropriate professional. About our editorial process.

Continue the field notes

Keep investigating

Suspected invasive pests