Common rust

What is common rust?

Common rust is a fungal disease caused by the Puccinia sorghi pathogen, which affects maize, wheat and barley crops, causing yield loss, especially in favourable environmental conditions. The disease thrives in moist, cool climates (16–25 °C) and slows or halts in hot, dry conditions.

Due to climate change, milder winters and warmer springs are causing earlier and more widespread outbreaks across the UK.

When infected, common rust forms orange-to-brown colour pustules (about 0.5–1.0 mm in diameter). The pustules darken over time and contain rust spores. 

What is the lifecycle of common rust?

The life cycle of common rust can involve up to five spore stages, which change under certain weather conditions. For example, white rust pustules change from buff to white when in high humidity conditions. 

Common rust fungus survives the winter as spores in high humidity conditions, spores are carried long distances by wind and have been found in the north of the UK. Rust development is favoured by high humidity with night temperatures of 65-70°F and moderate daytime temperatures. The disease is usually more severe on seed corn. 

The life cycle of common rust is somewhat weather-dependent as humid and windy certain conditions encourage the spread of the fungal pathogen.

The cycle follows these key steps:

Fungus overwinters – The fungus survives the winter as spores in high-humidity conditions. 

Spore dispersal – In spring and early summer, the spores are spread across large distances. 

Infection and pustal development – Spores land on leaves and infect plants. Reddish pustules form on leaves and turn black once matured, producing cinnamon-coloured spores. 

Secondary spread – Spores spread from plant to plant and field to field dispersed by wind, continuing the infection cycle.

Infected plant – The disease spreads, affecting more of the plant and potentially reducing yield.

Why is common rust a problem?

Common rust is a problem for plants in the UK because it thrives in mild, moist conditions, leading to increased infections, leaf discolouration, reduced growth, and potential plant death if left untreated.

Yield loss from common rust can be slight, only affecting crops up to 10% when the disease is severe however, rust spores are easily spread by wind causing rapid outbreaks.

How do you control common rust?

Effective control requires a multi-faceted approach, as crop rotation and tillage are ineffective (the disease does not overwinter in crop residue).

1. Choose hybrids resistant to common rust 

Hybrids with partial resistance to common rust typically produce fewer and smaller pustules as well as fewer fungal spores which can reduce the spread and impact of the disease on yield. 

We offer a range of extra early, very early, intermediate and late-maturing maize hybrid varieties. Find out more about our maize hybrids > 

2. Cultural control

Remove old plant debris that may host rust and inspect new plants for symptoms of common rust before cultivating.  If using a greenhouse, minimise humidity by increasing ventilation, spacing, and using fans, and monitor environmental conditions to avoid condensation. 

3. Consider a fungicide application

Fungicides will provide effective control against common rust when applied at the appropriate time in combination with cultural control measures.