Ascochyta leaf spot of sorghum

Ascochyta leaf spot is a fungal disease affecting sorghum crops, caused by the pathogen Ascochyta sorghi. This fungus is a member of the Coelomycetes group and is known for causing significant foliage damage across various climatic regions where sorghum is cultivated globally.

The primary host for this pathogen is the sorghum plant. While it generally targets leaves, severe infections can also affect leaf sheaths and occasionally stems. The disease significantly reduces the plant's ability to perform photosynthesis, which directly impacts biomass production and final grain yield quality.

The symptoms of the disease are characterized by lesions that appear on the leaf surface. Initially, these spots are small and light-colored with dark brown or reddish-purple margins. As the infection progresses, the lesions expand and coalesce, leading to necrotic areas. Within these spots, small black fruiting bodies known as pycnidia develop, which contain the fungal spores.

Environmental conditions play a critical role in the development and spread of Ascochyta sorghi. High humidity, frequent rainfall, and moderate temperatures are ideal for the rapid production and dispersal of spores. The pathogen survives during the off-season on infected crop residues left in the field and on contaminated seeds, serving as the primary inoculum for the next crop.

Effective management requires an integrated strategy to minimize the impact of the disease. Key practices include the use of disease-resistant sorghum hybrids and the implementation of crop rotation cycles to reduce the soil-borne inoculum. Proper field sanitation, including the deep burial of crop stubble and the use of fungicide-treated seeds, remains essential to maintaining healthy sorghum production throughout the growing season.