The Maize Downy Mildew Disease is a fungal disease of maize caused by the oomycete pathogens and is also known as Brown Stripe Mildew in Maize. This disease can cause extensive losses in hybrid maize varieties like Ganga-3. It is important to note that this disease can affect both seedlings and mature plants and occur during all maize growth stages. In addition, the disease can occur in both irrigated and non-irrigated fields.
Preventative strategies are important to reduce the risk of this disease and include proper crop rotation, the use of resistant varieties, and timely applications of fungicides. To effectively manage this disease, it is important to understand its disease cycle, the mode of disease spread, and the best methods for controlling it. This article will provide an overview and discussion of the Maize Downy Mildew Disease in Maize crops, including its symptoms, identification techniques, and control.
Maize/Corn Downy Mildew Disease Management
The Causal Organism of Maize Downy Mildew Disease
- Peronosclerospora maydis and Sclerophthora rayssiae are the commonly distributed downy mildew pathogens. They belong to the Family Peronosporaceae, Order Sclerosporales of the Phylum Oomycota.
- They produce sporangia at the tips of sporangiophores. In the beginning, Sporangia are white but turn to greyish light brown later. The sporangia germinate by protruding a germ tube, producing zoospores at a higher temperature.
The Disease Cycle of Maize Downy Mildew Disease
The disease cycle begins when the oospores of the pathogen primarily spread from soil and dormant mycelium in infected seeds. And the secondary spread occurs by many different mechanisms when the sporangiophores are spread by wind, splashing rain, and contact with infected plants.
The spores germinate, infecting the plant and forming a white, powdery coating (downy mildew) on the underside of the leaves. The downy mildew produces new spores spread by wind or splashing rain. These spores can then infect other plants, continuing the disease cycle. The disease is most severe when environmental conditions are warm and humid.
Occurrence of Maize Downy Mildew Disease in Maize Crop
- Location of Maize Downy Mildew disease: This disease occurs in maize crops in more than 40 countries. Some are Argentina, Brazil, Colombia, Mexico, Peru, Africa, India, the USA, and Thailand.
- Host range: The most common crops affected by downy mildew are cucurbits, such as cucumbers, squash, melons, and pumpkins, and other crops, such as celery, lettuce, spinach, and tomatoes, are also found to harbor this disease.
Favorable Conditions for Maize Downy Mildew Disease Spread in the Field
- The optimum conditions for downy mildew growth are low temperatures of 23-35°C, high relative humidity of 90%, wet leaves, and heavy dews. Wet leaves provide the ideal environment for the spores to germinate.
- A high population density of young maize plants in a small area can also contribute to the spreading of the disease, as the spores can easily be carried from one plant to the next by wind and rain.
- Poor air circulation can lead to the accumulation of moisture in the air, which can then cause the disease to spread more easily.