Peronosclerospora sacchari

Peronosclerospora sacchari is an oomycete pathogen belonging to the Sclerosporaceae family. It is a highly destructive, obligate parasite primarily known for infecting sugarcane and maize. As a major threat to agricultural productivity in warmer climates, it causes significant economic losses globally.

The primary disease associated with this pathogen is known as sugarcane downy mildew or crazy top. Infected plants exhibit distinct symptoms such as chlorotic streaking on leaves, stunted growth, proliferation of shoots (excessive tillering), and malformation of ears or tassels. In severe cases, the plant may fail to produce any viable grain or harvestable stalks.

The biology of the pathogen involves asexual reproduction through the formation of sporangia, which are disseminated by wind and water splash. Under nocturnal conditions of high humidity, white downy growth appears on leaf surfaces, containing conidia. Oospores, representing the sexual stage, form within leaf tissues and soil, acting as long-term survival structures that allow the disease to persist in fields.

Environmental conditions play a critical role in the epidemiology of Peronosclerospora sacchari. High relative humidity (exceeding 90%) and moderate temperatures (between 20°C and 28°C) are optimal for the rapid germination of conidia and successful host colonization. Frequent rainfall or heavy dew significantly accelerates the spread of the pathogen throughout a field.

Disease management requires a multifaceted approach due to the systemic nature of the infection. There is no curative treatment for already infected plants, making prevention paramount. Key control measures include the enforcement of strict quarantine regulations to prevent seed-borne spread, the development and deployment of resistant germplasm, and standard field hygiene practices to reduce inoculum pressure.

• Utilization of certified, disease-free seed stock.
• Systemic fungicide seed treatments to provide early protection.
• Roguing and disposal of infected plants during the early vegetative stage.
• Crop rotation with non-host crops to interrupt the infection cycle.