Lilac leaf mining moth

The caterpillars of lilac leaf mining moth feed within the leaves of lilac, privet and ash. This results in brown blotches on the leaves, the leaves then become rolled up from the tip.

Lilac leaf-mining moth

Quick facts

Common name: Lilac leaf-mining moth
Latin name: Caloptilia syringella
Plants affected: Lilac (Syringa), privet (Ligustrum) and ash (Fraxinus)
Main symptoms: Brown blotches and curled leaves.
Caused by: Caterpillar of a moth
Timing: June to September

What is lilac leaf mining moth?

Adult lilac leaf mining moths have brindled white and brown forewings and the wingspan is 10-13mm. The caterpillars feed within the leaves of host plants and are greenish white and up to 7mm long when fully grown.

Symptoms

The larvae initially cause a large blotch mine which soon goes brown and shrivels. Each mine is occupied by several caterpillars which later leave the mine and cause the leaf to become rolled up from the tip. The leaf roll is held in position by silken threads and the caterpillars complete their feeding inside. The caterpillars pupate in silken cocoons spun on the underside of the leaf and the second generation overwinter as pupae.

There are two generations a year with leaf symptoms occurring in June and August to September.

Control

Leaf damage from this moth is usually light and can be tolerated. Although the leaf mining may be considered unsightly, it is unlikely to affect the health or vigour of an established tree or shrub. In addition many leaf miners have parasites and predators which may be killed by spraying leading to a resurgence of the leaf miner or other invertebrates. In some areas birds such as blue tits have learnt to open leaf mine and feed on the caterpillars within. 

If desired light infestations on lilac trees can be dealt with by picking off and disposing of mined or rolled leaves, this can however, cause more damage than the leaf miner. Attacks on privet hedges can be much reduced by triming the hedge. In the autumn fallen leaves from a badly infested lilac can be gathered and burnt to reduce the number of overwintering pupae. The waste plant material can be disposed of in council waste. 

There are no insecticides that are suitable for controlling leaf mining insects in home gardens. 


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