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American Serpentine Leaf Miner

Liriomyza trifolii

American Serpentine Leaf Miner, Serpentine Leaf Miner, Chrysanthemum Leaf Miner, Celery Leaf Miner

The common name Serpentine Leaf Miner refers to several species of insect that mine the leaves of arable crops, vegetables and ornamental plants. They get their names after the characteristic mines the tiny larvae create when feeding within the plant. The mines twist and turn, looping like a serpent. As larvae grow, so does the larval mine, creating the serpents head. Liriomyza trifolii is a damaging pest in industry and agriculture, where it's now considered a cosmopolitan pest. Native to the Caribbean and the southeastern United States, it's now found on almost every continent!
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These flies are of considerable importance in terms of agriculture and economics.
Heavy infestations can be made less severe if the correct prevention strategies are implemented.


Adult: Mature flies are tiny (roughly 1-1.7mm!). The thorax is distinctively shiny-black, surrounded by yellow, with pale yellow faces and red eyes. Larvae: The maggots are colourless when first hatched. With each successive moult, they turn yellowish-orange and translucent. They appear like tiny, ovular maggots. Pupae: Cocoon-like structures are ovular, slightly flattened and dark brown. Eggs: The eggs are tiny and translucent and impossible to see with the naked eye.


Faded, meandering lines on the surfaces of leaves and pea pods are a tell-tale sign that a leaf miner insect is present. Feeding punctures on the surfaces of foliage. The mines for this species become wider as the larvae gets bigger. The mines are described 'snake-like'. Cells begin to die around the mines, resulting in brown patching. Areas of farmland with heavy infestations can sometimes appear burnt. The form and shape of mines can sometimes be influenced by the type of plant infested, the kind of leaf and the number of insect mines per leaf. Damaged foliage can sometimes appear stippled or speckled with white spots. Infestations can cause wilting in the plants affected. Larvae can sometimes be seen in leaf mines when the leaf is held over some light.











Endemic to South America; Introduced to North America, the Caribbean Islands, Africa, Asia, Europe and some Pacific Islands.

Biological treatment

Yellow sticky traps are an effective way to monitor fly populations. Alternatively, if you have a large patch, keep a count of the leaves found with mines. Regular monitoring can help with general assessment and decision-making regarding the next steps of action. Rational thinking may avoid unnecessary applications of pesticides and wasting money! Dispose of any leaves that have been mined or have eggs on them. Deeply infested leaves burnt when growing season terminates to destroy any persisting pupae. By practising good housekeeping in the garden, e.g. regularly pruning and clearing debris; you'll make your yard less attractive to pests. It's proposed that flies like this dislike strong-smelling herbs, such as lavender, thyme, lemon balm, fennel and basil. Planting these near your vegetable patches won't do you any harm! Another suggestion would be to grow plants beneath an insect-proof mesh. It's advised to rotate crops every year, and by doing so, infection by overwintering pupae will be less likely. Leaf mining flies have an abundance of natural enemies, so ideally, you want these to be controlling your pest populations. It's been found that areas with higher densities of these insects experience less severe symptoms from pests. These can be attracted to your green spaces using a few simple tricks. - Plant an array of indigenous plants, the more diversity, the better! - Install mini-habitats; leave out a pile of logs and sticks, a bucket of water, or, incorporate climbing plants in the garden. - Reduce your use of pesticides. When a leafminer infests a plant, one of the best modes of action is to encourage fast growth. Well-established plants that grow quickly can sometimes expel any eggs within the tissue. Crops with insufficient irrigation, water and fertilizer are much more prone to attack than a plant receiving the correct quantities.

Chemical treatment

It's advised only to take chemical action when all other options have been exhausted, and the infestation is considered severe. Insects such as leaf mining flies have a rapid rate of reproduction. There will always be flies left unaffected by chemical treatments, and this can lead to pesticide resistance. Pesticides containing abamectin, or pesticide 'spinosad', are proposed as the most effective components to fight this pest. Abamectin is thought to be the least damaging towards beneficial insects. Please read instructions carefully, taking care not to spray any plants that are in flower. Such pesticides can still show some degree of toxicity towards wildlife, so should be applied with extreme caution. Likewise, if you are planning to eat your harvest, make sure the food plant is listed on the bottle label and follow instructions. If you're ever feeling unsure, you can consult with your local garden centre or ask the wonderful Candide community for assistance!


These flies typically infest vegetable crops within the Cucurbitaceae, Fabaceae, and Solanaceae plant families. Please find a list below showing the most common plants to be infested.


Chrysanthemum spp.

A red flower with green leaves on a Phaseolus coccineus plant

Runner Bean

Phaseolus coccineus

A close up of a pepper on a Capsicum plant

Chilli / Peppers

Capsicum spp.


Dianthus spp.


Apium spp.


Cucumis spp.


Gerbera spp.

Baby's breath

Gypsophila spp.


Senecio spp.

Some red tomatoes on a Solanum plant


Solanum spp.


Medicago sativa

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