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Chrysanthemum leaf miner larvae make tunnels in the foliage of chrysanthemum and many other plants in the Asteraceae (daisy) family.
Common name Chrysanthemum leaf minerScientific name Chromatomyia (Phytomyza) syngenesiaePlants affected Chrysanthemum, Gazania, Senecio cineraria, ArgyranthemumMain cause Larvae of a leaf-mining fly tunnelling in the foliageTiming Mainly summer-autumn but can be all year round on glasshouse plants
Chrysanthemum leaf miner is a small fly that has larvae that feed by tunnelling in the leaves of its host plants.
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.
Light infestations can be dealt with by removing the affected leaves or crushing the larvae or pupae at the ends of the tunnels.
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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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