Northern corn leaf blight

Systematic position and biology: The pathogen Drechslera turcica (syn. Setosphaeria turcica) is a fungal organism that belongs to the genus Drechslera. It is a well-known plant pathogen responsible for causing Northern corn leaf blight, one of the most significant foliar diseases affecting maize production globally.

Disease symptoms and hosts: The primary host of the fungus is maize (corn). The disease is characterized by long, elliptical, necrotic lesions that appear on leaves. These lesions are typically greyish-tan in color. As the infection progresses, lesions expand and merge, eventually covering large portions of the leaf surface, which leads to tissue necrosis and reduced photosynthetic activity.

Life cycle of the pathogen: The pathogen survives the winter in infected crop debris on the soil surface as mycelium and conidia. During warm and wet weather, conidia are produced and spread to the new crop via wind or splashing rain. The fungus completes its infection cycle by penetrating leaf tissue, where it develops further, producing secondary inoculum that causes subsequent waves of infection.

Conditions for development and severity: The development of the disease is favored by temperatures between 20°C and 25°C and high humidity or prolonged periods of leaf wetness. If conditions are optimal, the damage can be severe. It leads to premature senescence of the foliage, poor grain filling, and reduced stalk strength, ultimately resulting in significant yield losses, sometimes exceeding 40-50% in susceptible hybrids.

Protection and management measures: Effective management of the disease requires an integrated approach. Farmers are encouraged to use resistant or tolerant corn hybrids as the first line of defense. Cultural practices such as crop rotation, removing or deep-tilling corn residues, and balancing nitrogen fertilization are essential. When disease pressure is high, the application of foliar fungicides at the V6 to VT growth stages can effectively minimize damage.