WHEN A MINER PROBLEM IS NOT A MINOR PROBLEM

The allium leaf miner is a garden pest that is spreading across the country and is especially detrimental to leeks. Dr Anton Rosenfeld, knowledge officer of Garden Organic, explains what to look for... and the best method of prevention

- Dr Anton Rosenfeld

I always remember leeks being an easy and reliable crop to grow. Unfortunately, it seems that these days this is no longer the case in many parts of the UK, where a relatively new pest is gradually spreading around the country. Allium leaf miner (Phytomyza gymnostoma) can cause serious damage to all alliums but is most noticeable in leek crops. It first arrived in the Midlands in 2002, and since then, has rapidly spread around the country. Despite being present for around 20 years, it is surprising how many growers are not aware of it, or how to deal with it.

IDENTIFY THE PROBLEM

The first obvious sign you have a problem with this pest is a pronounced twisting of the leaves.

This is most noticeable in leeks, and you will probably first notice it in late autumn. Later, the stems start to split, then eventually disintegrate, and in severe cases much of the crop is rotten before harvest time. Even mild infestations leave maggots and pupae in large enough numbers to render large parts of the crop inedible.