Unfortunately my leek crop has started to distort and when you open them up they have a small brown worm in them and brown marks all through the leek What is attacking the leek and is there anything I can do about it.
It's possibly leek moth larvae. Most sites say the caterpillars are green but Alys Fowler says creamy with brown head and legs. Another possibility is Allium leaf miner.
I had leak moth in my leeks and onions earlier in the year, i decided to harvest early while they were still only affecting the top growth. The caterpillars where off white with brown head as Bob has mentioned.
The cocoons of the Leek moth are brown.