Leek moth has two generations during the summer with larvae damaging the plants;
- From the first generation in May-June
- And the second generation in August-October
- The second generation is the more numerous and damaging
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.