The results of our 2024 survey into allium leaf miner – a small maggot that attacks allium crops – shows its spread north is limited.

We last surveyed the pest in 2017 and wanted to see how much it had spread since then. Survey participants suggested that allium leaf miner had spread slowly since, with limited spread northwards and no cases recorded across the border into Scotland. We’re not sure if this is because it's too cold, or it just hasn’t reached that far yet.

More people were covering their crops with mesh to protect against the pest than in the 2017 survey. And this suggests a greater awareness of allium leaf miner and a more proactive approach.

Allium leaf miner is a small maggot that attacks all alliums - but leeks are by far the most affected crop. This is because its growing period spans both the spring and the autumn, which are the two periods when the pest lays its eggs.

Most of the participants first noticed the pest within the last five years. However, there was a cluster of people who had first spotted the pest before 2011 around the Midlands – the area where it was first found.

For more in-depth analysis, read our full report. We're also doing a Members' Experiment about the effects of companion planting on allium leaf miner, read more here.