Crop Diseases - Leek Rust
This is a common disease of leeks occuring during most seasons. Mild infections are common and do little damage but severe infections may kill plants. Infections are clearly visible on leaves as orange or brown pustules which may be round or elongated. They are caused by the fungus Puccinia allii (also known as Puccinia porri). The pustules contain millions of spores which spread easily by wind to neighbouring plants. Warm and humid conditions encourage the fungus to spread.
Puccinia allii can also infect other plants in the same family (the allium family) such as garlic or onions.
The incidence and spread of rust on leeks can be reduced by a number of straightforward measures
- Good hygiene on your plot - make sure that any infected plant material is removed from your site rather than composted.
- Early action - if you spot an infection early enough remove infected plants (or infected areas of leaf) from your plot (make sure you wash your hands and anything else that might have been in contact with the infected plant tissue).
- Spacing - increasing spacing between leeks will allow better air flow and keep humidity from building up.
- Improve drainage on your site - this will help keep humidity down.
- Variety selection - although all leeks can be infected with Puccinia allii some varieties have partial resistance, such as Ardea, Porvite, Splendid, Walton Mammoth.
- Avoid excessive nitrogen inputs - lush growth caused by excessive nitrogen is more susceptible to rust infection. Complex organic material, such as compost, releases nitrogen slowly over a long period and so using compost rather than a synthetic fertilizer should avoid this problem.
- Make sure you have enough potassium - if your soil is low in potassium add a supplement high in potassium such as a seaweed dressing or an organic tomato fertilizer.
- Crop rotation - make sure leeks are planted as far away from last years growing site as possible.
Rusts also affect other plants such as beans, plums and some ornamentals (e.g. hollyhocks, iris). However, these are caused by different types of fungus and will not spread to leeks, onions or garlic.
