Allium Leaf Miner

This leaf mining fly is now well established throughout the Lichfield allotments, it attacks all Allium crops particularly leeks & onions. Whilst is has been identified in Europe for many years it did not arrive here until 2003 when it was discovered in Wolverhampton. This is now a very serious pest as it has the potential to totally destroy your crops during a heavy infestation, and at best it will render most plants inedible.

The picture shows the tell tale distorted leaves of onion plants during the early stages of grub attack. First generation adults emerge in late March - April and lay eggs around the base of leaves, or in the stalks of the plants. White/cream larvae hatch and feed inside the plant tissue before pupation. The pupae are 3-4mm long and orange or brown in colour. In leeks they are most easily found by peeling back the leaves when you will notice the brown tunnels or even the grubs and pupae. Second generation adults emerge October - mid November, lay their eggs and the cycle begins again. The pupae from this second generation is known to over-winter in the soil.

What can we do

The only known ways to defeat the pest is to

• Destroy all infected plants.
• Practise crop rotation.
• Only grow alliums under fleece or environmesh tunnels.
• Or delay planting until May - harvest before October.

Pat Bardon

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