Leeks have long been one of the vegetable plots most reliable crops; they are very versatile as a vegetable or in stews and soups, any surplus can be frozen.
Whilst not being of great show quality, I have found the easiest way of growing leeks is as follows:-
Sowing seeds in a prepared bed in March.
When the plants are the size of a pencil (typically early summer) transplant into a hole approximately 50mm diameter x 150mm deep formed with a dibber, no need to backfill merely water in, though some trimming of roots may be necessary.
Harvest during the period Nov – Mar.
About five years ago, my leeks began to wilt and collapse in late summer making the 250 leeks unusable! Crops in subsequent years have suffered the same fate.
The clue as to the cause was these grub type insects, which had burrowed between the leaves of the plant, further research led me to the cause, Allium leaf mining fly.
Allium leaf mining fly was first detected in Britain in 2002; it has become widespread in England and parts of Wales. The larvae bore into the stems and bulbs of leeks, onions, chives and garlic. Affected plants often develop secondary infections and rot.
The adult Allium leaf miner is a small fly, Phytomysa gymnostoma, but you are unlikely to spot it as it only 3mm long, and inconspicuous. The maggot-like larvae do the damage, by tunnelling into the leaves.
None of the pesticides currently available to home gardeners for use on leeks and onions will give effective control of leaf mining fly.
My research finds our only option is to protect the plants by covering them with an insect-proof mesh, at times when the adult flies are active and laying eggs. Peak adult activity is March to April and September to November. Crop rotation must also be used.
Doug Beds
Comments