Echinops leaf miner

The appearance of globe thistle (Echinops) foliage can be spoiled by the larvae of a fly that feeds within the leaves.

Leaf mines in <EM>Echinops</EM> foliage.

Quick facts

Common name Echinops leaf miner
Scientific name Phytomyza bipunctata
Plants affected Globe thistle (Echinops)
Main cause Larvae of a leaf-mining fly tunnelling in the foliage
Timing Spring and summer

What is echinops leaf miner?

Echinops leaf miner is a small fly which develops as larvae that feed within the foliage of wild and cultivated globe thistle (Echinops) plants.

Symptoms

The adult flies are ash grey and about 2mm long. They feed by rasping the leaf surface, causing many small pale spots on the upper leaf surface. More significant damage is caused by the creamy white larvae. They eat the internal tissues of the leaves and cause whitish brown discoloured blotches. The mines typically have a pale edge around the darker brownish centre.

There are probably at least two generations during the summer and by August leaves can be affected by several mines.

Control

Echinops plants will survive and produce flowers, even when there is extensive leaf mining, so control measures are not essential.

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. Suitable insecticides include acetamiprid (e.g. Bug Clear Ultra).

Plants in flower should not be sprayed due to the danger to pollinating insects.

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Biology

Echinops leaf miner has at least two generations during the summer. The females deposit their eggs on the foliage during April and July. The eggs hatch into legless larvae that tunnel into the foliage where they eat the internal tissues. The mines are linear forming silvery lines throughout the leaf, lines of black excrement (frass) are often visible within these mines. When fully fed, the larvae pupate within the mines.

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