Fusarium stalk and ear rot (Fusarium meridionale)

The fungus Fusarium meridionale is a significant phytopathogenic species belonging to the Fusarium fujikuroi species complex. It is a soil-borne and seed-borne pathogen responsible for various fungal diseases in agricultural crops, primarily causing root rots, stalk rots, and ear rots. This pathogen disrupts plant water uptake and nutrient transport, leading to systemic weakness and eventual crop death.

The primary hosts for this fungus include maize, wheat, and barley. The pathogen is widespread in regions with intensive agricultural production and survives in crop residues and soil, acting as a primary inoculum for subsequent planting seasons. Seed transmission also plays a crucial role in the initial colonization of young seedlings, often leading to pre-emergence or post-emergence damping-off.

Key symptoms include stunting of plants, chlorosis of lower leaves, and wilting during dry periods despite adequate soil moisture. In the later stages of development, internal tissues of the stem may turn reddish or brownish, often accompanied by characteristic white to pinkish mycelial growth. Ear rot in maize is characterized by the breakdown of kernel tissues and visible fungal growth, which makes the produce unsuitable for storage.

Environmental conditions play a decisive role in the disease cycle of Fusarium meridionale. High levels of humidity, frequent rainfall, and warm temperatures during the pollination and grain-filling stages are optimal for sporulation and infection. Insect damage to stems or ears often creates entry points for the fungus, significantly increasing the severity of the infection.

The economic impact of this pathogen is twofold: direct yield loss due to reduced grain weight and quality, and the contamination of grain with mycotoxins, such as fumonisins, which pose serious health risks to livestock and humans. Management strategies involve a multifaceted approach:

• Seed treatment with registered fungicides to control early-season infection.
• Crop rotation to reduce the level of inoculum in the soil.
• Effective residue management to speed up the decomposition of plant material.
• Cultivation of resistant or tolerant crop varieties.
• Application of foliar fungicides during critical stages of plant development.