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
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.
Echinops plants will survive and produce flowers, even when there is extensive leaf mining, so it is not necessary to control this insect. Leaf miners can be part of a healthy balanced garden, most species will have natural enemies including parasitoid wasps. Birds such as blue tits can sometimes open mines to consume the larvae within.
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.