Watch out for leek rust

Leek rust usually sets in during late summer to early autumn, so now is the time that you’re most likely to start seeing it. In this article we explain what it is, what to do, and how to prevent it in the future.

What is it & what does it look like?

Leek Rust is a fungus that develops on the leaves of any alliums – leeks, onions, garlic – and it’s not uncommon, especially at this time of year. It often occurs in beds where plants are overcrowded or where the soil is rich in nitrogen. You’ll recognise it by the brownish orange streaks or spots on the leaves of leeks, onions and garlic (as pictured)

What to do about it?

Once you see signs of leek rust on your leeks, don’t despair. You can still harvest your leeks and cook them – just peel off the affected leaves before you wash and chop them. If they’re not really ready to harvest yet, you can remove diseased leaves (being sure not to leave them lying on the soil) and give the plants a good watering. Try not to get water on the foliage though, just water them at the base. With luck they will continue to grow without too much further infection.

How to prevent it in the future…

  1. As mentioned, too much nitrogen does seem to be a problem, so try to avoid growing leeks in nitrogen-rich soil. Nitrogen can soften the leaves and make the plants more susceptible. If you use manure in the garden, you may find that your soil is quite high in nitrogen. Instead, try using a multi-purpose compost where you are planning on growing leeks.
  2. Give plants a little more space. Planting too closely together restricts air movement in and around the plants, and by increasing this you will minimise the risk of leek rust taking hold of your plants.
  3. Try to keep soil moisture consistent. Long dry spells followed by heavy rainfall don’t help when it comes to leek rust. Try to keep things even as much as possible.