Northern corn leaf blight

Northern corn leaf blight

Northern corn leaf blight (NCLB) is a plant disease that affects maize (corn) crops. It is caused by the fungal pathogen Exserohilum turcicum, previously known as Helminthosporium turcicum. This disease is prevalent in temperate and tropical regions where maize is cultivated, leading to significant yield losses if not managed properly.

Symptoms

The primary symptoms of Northern corn leaf blight include the appearance of long, elliptical, grayish-green to tan lesions on the leaves of the maize plant. These lesions can range from 1 to 6 inches in length and may coalesce to cover large areas of the leaf surface. As the disease progresses, the lesions can cause the leaves to die prematurely, reducing the photosynthetic capacity of the plant and ultimately affecting grain fill and yield.

Disease Cycle

The pathogen Exserohilum turcicum survives in crop residue and soil, where it produces spores that can infect new maize plants. The disease cycle begins when spores are dispersed by wind or rain splash to the leaves of susceptible maize plants. Infection is favored by moderate temperatures (64-81°F) and high humidity or prolonged leaf wetness. The fungus penetrates the leaf tissue and begins to produce lesions, which can release more spores to continue the cycle.

Management

Effective management of Northern corn leaf blight involves an integrated approach, including:

• **Resistant Varieties**: Planting maize hybrids that are resistant to NCLB is one of the most effective strategies.
• **Crop Rotation**: Rotating maize with non-host crops can help reduce the inoculum levels in the soil.
• **Tillage**: Burying crop residues through tillage can reduce the survival of the pathogen.
• **Fungicides**: Application of fungicides can be effective, especially in environments conducive to disease development. Timing of application is critical for maximum efficacy.
• **Field Scouting**: Regular monitoring of fields for early detection of symptoms can help in timely management decisions.

Economic Impact

Northern corn leaf blight can cause significant economic losses in maize production. Yield losses can range from 30% to 50% in severe cases, depending on the susceptibility of the hybrid, environmental conditions, and the timing of infection. The cost of fungicide applications and other management practices also adds to the economic burden on farmers.

Research and Development

Ongoing research aims to develop more resistant maize hybrids and improve understanding of the pathogen's biology and epidemiology. Advances in genetic engineering and molecular biology are also being explored to enhance resistance and develop more effective management strategies.

See Also

• Maize
• Plant pathology
• Fungal diseases of plants
• Crop rotation
• Fungicide