Agriculture

Maize/Corn Downy Mildew Disease Management: Symptoms, Treatment, Chemical, Biological, Natural, and Organic Control

Table of Contents [show]

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.

Maize/Corn Downy Mildew Disease Management

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.

In case you missed it: Maize Rust Disease Management: Symptoms, Treatment, Chemical, Biological, Natural, and Organic Control

Maize Disease

Symptoms of Maize Downy Mildew Disease

  • This disease is characterized by chlorotic spots on the leaves, followed by a white, downy-like cottony fungal growth on the underside of the leaf. These downy patches eventually spread to the upper side of the leaf, forming yellow-brown lesions as the disease progresses and causing the death of plants.
  • In severe cases, the leaves may become yellow and die prematurely, reducing yields. The fungus can infect the stems and ears of the plants, causing further losses.
  • The infected plants remain stunted and show a bushy appearance due to reduced internodal length.
  • The leafy outgrowths in the tassel and the growth of auxillary buds on the stalk of the tassels and cobs result in the crazy top appearance.
  • The infected maize plants exhibit yellowing and wilting of leaves, stunted growth, and reduced grain yields.

Percentage of Yield Loss due to Maize Downy Mildew Disease in Maize Crop

  • In India, the yield losses due to maize downy mildew disease range from 20-50%. In Bangladesh, the yield losses range from 10-30%. In Mexico, the yield losses range from 10-25%. In the United States, the yield losses range from 10-30%.
  • In Canada, the yield losses range from 5-15%. In Africa, the yield losses are 15-40%. Generally, the ETL for maize downy mildew is set at 5% disease incidence in the field.

Cultural Control measures of Maize Downy Mildew Disease

  • Sanitation: It involves removing crop residues from the field and cleaning equipment after harvest to reduce the number of spores and fungi available to cause infection.
  • Crop rotation: Rotating maize with other crops, such as pulses, can help decrease the disease pressure.
  • Tillage: Deep ploughing can help control the spread of the disease by exposing the infected plant material to scorching sun and reducing the amount of available inoculum on the soil surface.
  • Resistant carieties: Growing resistant varieties and TNAU hybrids of maize like  CO-1, COH-1, COH-2, and COH-6  can help reduce the impact of downy mildew.
  • Roguing out: Removing and burning the infected plants is necessary to prevent the spread of this disease throughout the field.

Biological Control measures of Maize Downy Mildew Disease

Fungal antagonists: Several fungal antagonists have been identified to have the potential for downy mildew management. One example is Trichoderma spp., which produces compounds that can inhibit the growth of the pathogen. It can be applied as a seed treatment or sprayed on maize plants’ leaves.

Bacterial antagonists: Several bacteria have been found to have the potential for downy mildew management. For example, Pseudomonas syringae can produce compounds that inhibit the growth of the pathogen. It can be applied as a seed treatment or sprayed on maize plants’ leaves.

Viral antagonists: Several viruses have been found to have the potential for downy mildew management. For example, the Cucumber mosaic virus (CMV) and Tobacco mosaic virus (TMV) effectively control downy mildew. It can be applied as a seed treatment or sprayed on maize plants’ leaves.

Biopesticides: Several biopesticides have been developed for downy mildew management. These include formulations of Bacillus subtilis and Neem Oil. That can be applied as a seed treatment or sprayed on the leaves of the plants.

Chemical Control measures of Maize Downy Mildew Disease

  • Soil application – Mix 2.5kg of P. fluorescens (or) T. viride with 50 kg of well-decomposed FYM or sand ten days before application and distribute the mixture uniformly 30 days after sowing.
  • Seed treatment – Treat the seeds with Metalaxyl at 6 grams/kg.
  • Spray application – Apply systemic fungicides like Propamocarb or Metalaxyl of 1kg or Mancozeb of 2 grams per liter on the 20th day after sowing.

Preventive Measures for Control of Maize Downy Mildew Disease

  • Crop monitoring – Regularly monitoring fields for signs of disease will help to catch and manage it early before it spreads.
  • Planting disease-free seed – Planting disease-free seed is essential in preventing the spread of Maize Downy Mildew Disease. It is important to ensure the seed is free of any fungal diseases before planting.
  • Avoiding overhead irrigation – Overhead irrigation can help to spread the disease. Therefore, it is important to avoid using overhead irrigation when possible.
  • Pruning – Pruning can help to reduce the spread of the disease. Pruning off infected leaves can help reduce the number of fungal spores on the plants.

In case you missed it: Maize Shoot Bug Pest Management: Symptoms, Treatment, Chemical, Biological, Natural, and Organic Control

Maize Farming

Conclusion

In conclusion, maize downy mildew is a serious disease that can cause major crop losses. Although the disease can be managed through cultural practices and chemical control measures, the best way to prevent its spread is to practice crop rotation and maintain healthy soil fertility. Therefore, with the proper implementation of integrated approaches, farmers can protect their maize crops from the devastating effects of maize downy mildew.

Last Updated:
Author: Reddy

LEAVE A REPLY

Please enter your comment!
Please enter your name here