Fusarium stalk rot of sorghum

The fungus Fusarium thapsinum is a primary plant pathogen responsible for stalk and root rot in sorghum crops. It is a filamentous fungus that belongs to the Ascomycota phylum. It survives as a saprophyte in the soil and on crop debris, making it a persistent threat in agricultural environments where sorghum is cultivated continuously.

The primary host for this pathogen is sorghum (Sorghum bicolor). The fungus infects the plant throughout its lifecycle, starting from seed germination and continuing through to grain maturation. It is particularly known for infecting the stalk tissue and the developing panicle, which directly impacts the economic yield and quality of the harvested grain.

The clinical signs of the infection include internal discoloration of the stalk pith, which often turns reddish-purple or brown. As the disease progresses, the structural integrity of the plant weakens, leading to lodging. In humid conditions, mycelial growth may appear on the surface of infected tissues, and the grain may show signs of discolouration or moldiness.

Environmental conditions play a crucial role in the development and spread of Fusarium thapsinum. The disease is favored by warm temperatures, typically ranging from 25°C to 30°C, combined with high humidity levels. Plant stress, caused by drought, poor soil fertility, or insect infestation, significantly predisposes the crop to successful colonization by the fungus.

Effective management strategies against this disease require a multi-faceted approach. Key practices include:

• Utilizing disease-resistant sorghum hybrids.
• Implementing long-term crop rotation to break the disease cycle.
• Using high-quality, fungicide-treated seeds.
• Optimizing irrigation to reduce plant stress.
• Proper disposal of crop residues to reduce the inoculum load in the field.