Leek Rust, Allium Rust
Rust is a widespread and common group of pathogenic fungi of the order Pucciniales. Puccinia porri is a type of Rust that affects Alliums. P. porri can be split into smaller sub-categories, each affecting different Allium plants depending on what part of the world you're growing in. Characteristic of Rust fungi is the appearance of orange-brown pustules of the foliage of plants. Leek Rust arises as slit-shaped spots, on the sheaths and stems of Leeks. Allium Rust tends to arise during mid-Summer, becoming less frequent when the weather cools. Although, outbreaks of the disease can be common during milder periods of Autumn. In the UK, P. Porri is most common in Leek, Garlic and Chive, with onions and ornamental species seldom impacted.
Small, slit-like or ovular orange pustules on leaves and sheaths.
In worst cases plants can die.
Never compost diseased materials.
It has been suggested that the disease occurs more when soils possess too much nitrate. Potash can be applied to the soil to help reduce nitrate levels. Any Allium weeds with potential to harbour the disease should be removed promptly. Allow plenty of space between plants and provide sufficient drainage. If Leeks, Chives and Garlic begin to show pustules, then apply Vaseline to prevent the spread of spores. Make sure tools and boots are cleaned between visiting different allotments and gardens. If a bad attack is experienced, a long period of crop rotation is advised. It's recommended to wait between 4-5 years before using the site again for growing Leek, Garlic and Chive. More resistant cultivars include 'Walton Mammoth', 'Apollo', 'Poribleu', 'Autumn Poristo', 'Spendid' and 'Titan'.