Downy mildew of maize and sorghum

Downy mildew, specifically caused by the pathogen Peronosclerospora miscanthi, is a severe systemic disease affecting various graminaceous crops. As an oomycete, it thrives by colonizing the vascular system of the host, which leads to permanent physiological disruption and significant yield reduction in infected fields.

The primary hosts for this pathogen include maize (corn) and sorghum, as well as sugarcane. While the term downy mildew is broad and applies to other crops like raspberries, strawberries, or oilseed rape, P. miscanthi is highly specialized in its host range, focusing on warm-season grasses and causing distinct symptoms of systemic infection.

Symptoms typically include chlorotic stripes along the leaf blades, stunted growth, and a characteristic white, fuzzy appearance on the underside of leaves during humid conditions. Infected plants often fail to produce viable ears or panicles, showing symptoms of severe stunting and leaf distortion that significantly weaken the crop stand.

The development of the disease is strictly dependent on environmental conditions, particularly high humidity and moderate temperatures, which facilitate the production and dispersal of sporangia. The pathogen overwinters primarily in crop debris and the soil, making field sanitation a critical component of the management strategy for this disease.

• Planting certified disease-free, resistant corn and sorghum hybrids.
• Implementing strict crop rotation to break the pathogen's life cycle.
• Deep plowing to bury infected crop residues and accelerate decomposition.
• Using systemic seed treatment fungicides to provide early-stage protection against infection.