Chrysanthemum leaf miner

Chrysanthemum leaf miner larvae make tunnels in the foliage of chrysanthemum and many other plants in the Asteraceae (daisy) family.

Mines on chrysanthemum leaves

Quick facts

Common name Chrysanthemum leaf miner
Scientific name Chromatomyia (Phytomyza) syngenesiae
Plants affected Chrysanthemum, Gazania, Senecio cineraria, Argyranthemum
Main cause Larvae of a leaf-mining fly tunnelling in the foliage
Timing Mainly summer-autumn but can be all year round on glasshouse plants

What is chrysanthemum leaf miner?

Chrysanthemum leaf miner is a small fly that has larvae that feed by tunnelling in the leaves of its host plants.

Symptoms

The larvae feed inside the leaves and create long sinuous tunnels that show on the upper leaf surface as white or brown meandering lines. On host plants with small leaves, such as Argyranthemum and Pyrethrum, all of the inside of the leaf may be consumed, so the whole leaf becomes discoloured and dries up.

The adult fly is 2-3mm long and brownish black in colour. The females scrape the leaf surface to feed on exuded sap, which causes small pale spots on the upper leaf surface. The larvae are creamy white legless maggots up to 3-4mm long. The pupal stage is pale brown and the pupae can be found in the leaves at the ends of the mines.

The leaf mines created by the fly's larvae disfigure the leaves and heavy infestations can cause a significant loss of foliage. Plants can be attacked in both gardens and greenhouses. The heaviest infestations are generally indoors.

Control

Non-chemical control

Light infestations can be dealt with by removing the affected leaves or crushing the larvae or pupae at the ends of the tunnels.

Chemical control

  • It is very difficult to achieve control of leaf miners with insecticides
  • If plants become extensively infested a systemic insecticide that may kill the larvae inside the leaves can be used. One systemic insecticide is available to home gardeners the neonicotinoid acetamiprid (e.g. Bug Clear Ultra)
  • Plants in flower should not be sprayed due to the danger to pollinating insects
  • Inclusion of a pesticide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener

Download

Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

Biology

On outdoor host plants there are usually two generations of chrysanthemum leaf miner a year, with damage occurring in early summer and late summer-autumn. In heated greenhouses or on susceptible house plants, this fly can continue breeding throughout the year.  Eggs are laid singly on the foliage. On hatching, the larva bores into the leaf, where it eats out a tunnel between the upper and lower leaf surface. When fully fed, the larva pupates at the end of its tunnel.

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