Downy mildew of pearl millet

The causative agent of this disease is the oomycete Sclerospora graminicola, which causes systemic infection in cereal crops. The pathogen persists in the soil primarily as oospores, which are highly resilient structures capable of surviving in the environment for several years, making the disease difficult to eradicate through crop rotation alone.

While pearl millet is the primary host, the pathogen also affects several wild grass species. Primary infection typically occurs through the roots of young seedlings, favored by high soil moisture and moderate temperatures, which trigger the germination of the overwintering oospores near the developing root system.

Symptoms of the infection include chlorotic streaks on the leaves, which eventually turn yellow. A diagnostic feature is the presence of white, downy fungal growth on the underside of the leaves. In advanced stages of infection, plants may exhibit severe malformation, such as 'green ear' symptoms, where floral parts are transformed into leafy structures, rendering the plant sterile.

The spread of the disease is highly dependent on environmental conditions, particularly humidity and rain, which facilitate the production and dispersal of sporangia. These spores are wind-borne and can spread the infection throughout a field in a relatively short period, especially under conditions of high density and poor air circulation among the crops.

The economic impact of downy mildew is significant, leading to severe yield losses due to plant stunting, tiller failure, and complete sterility of the panicles. Infected crops show reduced biomass and grain quality, making it essential to implement integrated pest management practices to maintain agricultural productivity.

• Use of certified, disease-free seed lots.
• Planting resistant or tolerant millet cultivars.
• Application of seed-dressing fungicides to protect seedlings.
• Implementing deep plowing to bury crop residues.
• Maintaining proper field sanitation to reduce primary inoculum.