Drechslera leaf blight of maize

The fungus overwinters as mycelium and conidia on infected crop residues left on the soil surface, as well as in soil or on the seeds of infected maize plants.

Primary infection occurs when conidia are spread by wind or rain splash onto the leaves of emerging corn plants during the spring season under suitable moisture conditions.

The pathogen prefers high humidity and temperatures ranging from 20°C to 30°C for optimal conidial production and secondary infection cycles throughout the growing season.

Accurate identification is typically confirmed through laboratory isolation and microscopic observation of the characteristic conidia produced on the leaf lesions.

The pathogen infects all aerial parts of the maize plant, including leaves, leaf sheaths, stalks, and the husks of the ears, leading to significant physiological stress.

Seedling blight may occur if infected seeds are planted, resulting in reduced stand establishment and lower overall plant density in the field.

In mature plants, severe leaf blight reduces the photosynthetic surface area, leading to poor grain fill and lower yields in terms of both weight and quality.

Infection of the ears and kernels can lead to the development of ear rot, which compromises the seed viability and makes the harvest susceptible to mycotoxin accumulation.

The total yield loss caused by this disease is dependent on the timing of infection and the susceptibility of the hybrid, often ranging from 10% to 25% in favorable years.

Symptoms typically start as small, yellow-to-tan spots that gradually expand into elongated, spindle-shaped lesions parallel to the leaf veins.

The center of the lesions often turns gray or olive-brown, and under high humidity, a velvety layer of conidia becomes visible to the naked eye.

On stalks and leaf sheaths, the lesions may coalesce into larger necrotic areas, which can lead to weakened stems and increased vulnerability to lodging.

Grain infection manifests as dark brown or black lesions on the kernels and husks, often accompanied by fuzzy fungal growth during storage if moisture levels are high.

• Spindle-shaped necrotic lesions on leaves.
• Velvety olive-colored spore masses.
• Premature yellowing and drying of lower leaves.
• Necrosis of the husk and silk tissues.
• Reduced grain filling and lightweight cobs.

The most effective strategy is the deployment of resistant or tolerant corn hybrids, which significantly limits the pathogen's ability to colonize host tissues.

Crop rotation and deep tillage help bury infected crop debris, reducing the initial inoculum pressure for the subsequent maize planting season.

Seed treatment with high-quality systemic fungicides protects the emerging seedlings from soil-borne and seed-borne infection during the critical early growth stage.

Foliar application of fungicides during the vegetative growth stages can be effective if environmental conditions favor the rapid spread of the disease.

Field sanitation, including the destruction of harvest residues and effective weed control, helps minimize the overwintering potential of the fungal population.