Brown stripe downy mildew

Brown stripe downy mildew, caused by the oomycete Sclerophthora rayssiae, is a significant disease affecting maize crops globally. Unlike true fungi, this pathogen belongs to the oomycetes group, which thrives under specific moisture conditions, making it a persistent challenge for farmers in certain geographic regions.

This pathogen primarily targets maize, causing systemic or localized infections depending on the timing of initial exposure. When conditions are conducive to infection, the pathogen can spread rapidly throughout a field, impacting both the physiological development and the final yield potential of the corn plants.

Symptoms are identified by the development of narrow, chlorotic stripes that gradually turn brown or reddish-brown. As the disease progresses, these stripes may coalesce, causing significant tissue necrosis. Under conditions of high relative humidity, a fine, whitish growth representing the pathogen's reproductive structures may be visible on the underside of the leaves.

The infection cycle is heavily dependent on wet conditions. Zoospores require free water, such as rain or irrigation runoff, to mobilize and infect the host plant. The pathogen survives in the soil as oospores, which remain viable in crop debris or the soil matrix, serving as the primary source of inoculum for subsequent seasons.

The economic impact of brown stripe downy mildew can be severe, leading to stunted plants, poor ear development, and significant yield losses. Effective management requires an integrated approach, focusing on breaking the infection cycle through cultural practices and, when necessary, the application of targeted fungicides.

• Implementing crop rotation to reduce soil-borne inoculum.
• Selecting and planting resistant or tolerant maize hybrids.
• Improving field drainage to reduce surface water accumulation.
• Removing and destroying infected crop residues after harvest.
• Applying systemic fungicides at the early stages of disease appearance.