Northern corn leaf blight

Exserohilum turcicum is a significant fungal pathogen belonging to the genus Exserohilum, responsible for Northern Corn Leaf Blight (NCLB). This disease primarily affects maize, although it can also infect sorghum and other related grasses, causing severe foliar damage throughout the growing season.

The infection manifests as long, cigar-shaped necrotic lesions on the leaves, which start as small spots and gradually expand. In favorable conditions, these lesions become gray or tan, eventually merging to kill large portions of the leaf tissue. The presence of dark, olive-colored sporulation on the underside of the leaf is a classic diagnostic feature.

The disease cycle of this pathogen relies on primary inoculum overwintering in infested crop debris. During the growing season, conidia are dispersed by wind and splashing rain to healthy leaves. High humidity, heavy dew, and moderate temperatures ranging between 20°C and 28°C create the ideal environment for the rapid reproduction and spread of the fungus.

The virulence of the pathogen is highly dependent on the susceptibility of the hybrid and the timing of the infection. Early-season infections, especially before the silking stage, are the most destructive, as the loss of photosynthetic area severely restricts the plant's ability to fill the kernels, resulting in significant yield losses.

Integrated management is essential for controlling NCLB. This includes planting resistant or tolerant corn hybrids, which is the most effective defense. Additionally, farmers should implement crop rotation to break the infection cycle, practice deep tillage to bury infected residues, and apply fungicides when environmental conditions favor disease development.

• Selection of resistant or moderately resistant corn hybrids.
• Implementation of crop rotation with non-host crops.
• Tillage practices that promote the decomposition of corn residues.
• Timely scouting and fungicide applications during early infestation.