Corn late wilt pathogen

The fungus survives in the soil and on crop residues as mycelium and chlamydospores. It is capable of long-term survival under adverse environmental conditions, making it an extremely persistent pathogen in crop rotation.

For laboratory identification, the fungus is isolated on growth media, where it forms colonies with characteristic conidiophores and oval-shaped conidia.

Microscopic examination allows for precise species identification based on spore morphology, which is critical for distinguishing it from other types of root rots and fusarium species.

Molecular genetic diagnostics, including PCR testing, is the most accurate method for confirming the presence of this pathogen in infected maize tissue samples.

The primary crop affected by this pathogen is maize (corn). The fungus enters through the root system and spreads via the xylem, effectively blocking the transport of water and nutrients.

Infection can occur at various vegetative stages, but the most active fungal development is observed during the grain formation and filling period.

In addition to maize, the pathogen has a wide host range among cereal crops, which complicates control efforts in areas with intensive agriculture.

Infection leads to premature plant death, which reduces the thousand-kernel weight and results in significant yield losses in infested fields.

Under high inoculum pressure, not only is grain weight reduced, but grain quality also deteriorates, rendering the product unsuitable for long-term storage.

Disease development is most intense during hot and dry periods in the second half of the summer, when plants experience water stress, which facilitates the rapid movement of the fungus through the vascular bundles.

High soil temperatures combined with moisture deficits create optimal conditions for the activation of fungal spores and subsequent infection of maize root hairs.

Early symptoms of the infection may be subtle, but as the crop approaches the dough stage, signs become increasingly visible across the entire field.

The spread of the pathogen within crops is exacerbated by improper irrigation management, where cycles of drought and excessive watering weaken the plant's immune system.

In the autumn, after harvest, the pathogen actively colonizes crop residues, forming structures for overwintering in the top layers of the soil.

A key sign is late wilt, which manifests as rapid yellowing of the lower leaves, gradually spreading upward along the stem.

A characteristic symptom is the presence of clearly defined necrotic stripes on the stems, within which the pith is found to be destroyed, often accompanied by a whitish fungal mycelium.

When cutting the stem in the lower section, one can observe darkening of the vascular bundles and specific tissue discoloration caused by the fungus's metabolic products.

Plants affected by the disease often lodge due to the destruction of the internal stem structure, which significantly complicates mechanical harvesting.

In later stages, numerous small black dots — pycnidia or sclerotia — may form on the lower part of the stem, indicating the completion of the fungal life cycle.

The primary method of control is the implementation of crop rotation cycles, incorporating non-host crops such as legumes or oilseed rape.

• Use of resistant maize hybrids.
• Thorough shredding and deep incorporation of crop residues into the soil.
• Application of fungicidal seed treatments before planting.
• Optimization of irrigation schedules to prevent moisture stress.

Chemical control on growing plants is difficult due to the systemic nature of the disease, so the focus remains on preventive measures and good agricultural practices.

Weed management is essential, as certain weeds act as reservoirs for the pathogen during the off-season, helping to keep inoculum levels in the soil low.