Northern leaf blight

What is northern leaf blight ? 

Northern leaf blight disease (Exserohilum turcicum) is a yield-limiting disease that affects maize crops. The disease is most prevalent during moderate temperatures (17°C to 27°C) with prolonged periods of moisture and typically appears at or after silking. Yield losses are most severe when northern leaf blight infects maize plants early and reaches the upper leaves by the beginning of ear fill. 

When infected, northern leaf blight forms elliptical, grey to tan lesions on leaves that range from 1 to 6 inches long. Infection often starts from the lower leaves where humidity is highest, northern leaf blight spores coat the area and give it a dark, dirty appearance. This may cause plants to lose their lowest leaves, weakening the crop and reducing yields. Northern leaf blight management strategies are often used to combat the disease.

What is the lifecycle of northern leaf blight?

The life cycle of northern leaf blight is somewhat weather-dependent as certain conditions encourage the spread of the fungal pathogen between maize plants. The cycle follows these key steps:

1. Fungus overwinters – The fungus survives in infected plant debris, such as leaves and husks, as mycelia and conidia (spores).
2. Spore dispersal – In spring and early summer, conidia are spread to new leaves by wind and rain.
3. Infection and symptom development – Once on the leaves, the fungus infects the plant under favourable conditions, leading to symptom development, including lesions.
4. Secondary spread – Spores from leaf lesions are further dispersed by wind and rain, continuing the infection cycle.
5. Infected plant – The disease spreads, affecting more of the plant and potentially reducing yield.

This cycle repeats each season. Heavy dews, frequent light showers, high humidity, and moderate temperatures increase the spread and development of northern leaf blight disease. Lesions on the ear leaf and significant loss of green leaf area can result in yield loss, emphasising the role of environmental conditions in disease progression and the need for adequate disease control. 

Why is northern leaf blight a problem?

Yield loss from northern leaf blight can be significant, resulting in a loss of as much as 30% to 50%. If lesions appear on the ear leaf 2 weeks before, or 2 weeks after tasseling and conditions are favourable for disease development, this will see the greatest yield loss. 

In severe cases of northern leaf blight, lesions can merge together across large areas of leaves causing excessive blighting. This can reduce the photosynthetic capacity of the leaves, causing the plant to draw on stalk reserves to finish grain fill, leaving plants prone to stalk rot and standability issues.

How do I control northern leaf blight?

The best strategy to reduce yield loss from northern leaf blight is by using multiple management methods. 

1.  Choose hybrids resistant to northern leaf blight

Hybrids with partial resistance to northern leaf blight typically produce fewer and smaller lesions 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 

Varietal resistance, although limited, can contribute to reducing infection levels.

Pioneer Research Hybrid Northern Leaf Blight Resistance Scores 2024

(9 = Resistant, 1 = Susceptible)

• P7179 (4)
• P7326 (4)
• P2847 (4)
• P7034 (5)
• P7381 (4)
• P7647 (5)

2. Reduce previous maize residue

Reduce maize residue by rotating crops or utilising any form of tillage that places soil in contact with maize residue. This promotes decomposition and decreases the amount of disease residue that survives to the subsequent cropping season. Reducing maize residue however, does not protect against spore showers carried into a field on wind currents.

3. Plant at the right time

Planting maize on time can help it grow faster than the disease spreads, reducing severe damage. Late-planted maize is more vulnerable because it gets infected earlier when plants are smaller. However, in severe outbreaks, both early- and late-planted maize can still be heavily affected.

4. Consider a fungicide application

Approved foliar fungicides are available to help control or suppress northern leaf blight development.