Autumn is a great time for harvesting leeks, but they’re not always in tip-top condition when it comes to pulling them up. Here are a few possible problems that you may encounter…
If you start to see orange-brown marks appearing on the foliage, it is probably leek rust, a fungus that develops on the leaves of any alliums – leeks, onions, garlic – and it’s not uncommon, especially at this time of year.
If yours are affected, it is best to pull up your leeks and you can still eat them once affected foliage is removed. To prevent it in the future, try not to overcrowd plants, and do not use a liquid feed.
Leaves that have white, papery strips like these are a sure sign of Leek Moth damage. The moths lay their eggs, the eggs hatch and the caterpillars feed off the leeks. You may be able to see the caterpillars, or the cocoons as well as the damage to foliage.
If this is a problem in your patch, try rotating crops next season and grow leeks under insect proof mesh netting or fleece.
Allium Leaf Miner
This fly lays its eggs on leeks, onions and other alliums, and when the maggots hatch they eat little tunnels from the leaves, leaving a trail behind them.
Again, if this is a problem in your plot, rotate crops next season and grow leeks (and onions/garlic) under insect mesh.
Onion White Rot
This is another fungal disease that can be a real nightmare if it takes hold. You may first see leaves turning yellow, and then at the base of the plant a white fluffy mould (it’s not very clear in our picture, so do a quick google if you’re unsure as there are better photos out there that will help you to diagnose it!)
Annoyingly, the fungal spores live in the soil and can last quite a long time…up to 15 years sometimes! If it has hit your plot, then the best option is to not grow onions/leek/garlic for a few seasons and keep adding plenty of organic matter to your soil to help it recover itself.