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Leek moth is mainly a problem in southern England but it is spreading north. The caterpillars feed within the foliage and stems or bulbs of leeks, onions and related vegetables.
Adult leek moth is an inconspicuous small (5-6mm) brown moth. Its larvae (caterpillars) feed on leeks and similar crops.
Damage from leek moth caterpillars appears as;
Note that these plants are also attacked in a similar manner by larvae of a fly, known as the allium leaf-mining fly (allium leaf-miner);
The female moths can be prevented from laying eggs by covering susceptible plants with insect-proof mesh. Crop rotation should also be practised to prevent potential build-up of moth populations under the fleece. The mesh should be kept in place for the entire growing season.
Look for the white, net-like silk cocoons on the foliage and squash them.
None of the pesticides currently available to home gardeners for use on leeks and onions will give effective control of leek moth.
Leek moth has two generations during the summer with larvae damaging the plants;
Initially the caterpillars mine the foliage but the older larvae bore into the stems and bulbs.
When fully fed, the caterpillars are 11 mm long. They exit the plant and pupate within net-like silk cocoons that are spun on the foliage.
Adult moths emerge in autumn and overwinter in sheltered places.
Allium leaf miner
Leek moth (UK moths)
Onion white rot
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