Agriculture

Common Rust Disease Management in Maize: Symptoms, Treatment, Chemical, Biological, Natural, and Organic Control

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Common Rust Disease, also known as Puccinia sorghi, is a fungal pathogen that affects maize plants. It first appears as chlorotic specks on the leaves, followed by the development of golden-brown pustules on the ground surface of the plant tissue. These bumps contain urediniospores that can spread and cause further infection. Over time, the bumps change from brown to black and become teliospores. The disease can also develop on other parts of the plant, such as husks, tassels, and stalks.

Common Rust Disease Management in Maize

Common Rust disease management in Maize

The causal organism of Common Rust disease 

Common Rust Disease of maize is caused by the fungus Puccinia sorghi. The fungus overwinters in an alternate host, a species of Oxalis, and releases fragments in the spring that can be transported by wind and rain to infect maize plants. The disease is favored by high relative humidity, dew, rain, and cool temperatures (around 15 to 20°C), while hot, dry weather slows or hinders its development.

The disease mainly affects maize plants used for seed production and sweet corn, reducing their yield due to lower plant productivity and lodging. However, maize crops used for livestock feed, industrial products, or processed foods are not as affected by this disease.

The disease 

Common Rust Disease of maize is caused by the fungus Puccinia sorghi, which has five different spore stages: teliospores, basidiospores, pycniospores, aeciospores, and urediniospores. Viable urediniospores travel to the north from warmer southern climates each year. Still, since the disease is an obligate parasite, it cannot overwinter in northern US states. The severity of the disease depends on weather conditions, and the number of spores carried north each season.

Urediniospores infect maize leaves and produce secondary inoculum leading to a polycyclic disease cycle, producing basidiospores that infect Oxalis and then produce pycniospores and aeciospores, which are wind-blown to maize and cause infection. Urediniospores measure 22-33 × 20-28 µm, while teliospores are two-celled and measure 27-53 µm.

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Maize Farming

Causes/conditions favorable for Common Rust disease spread in the field

  • Disease development of Common Rust Disease of maize is favored by cool, moist weather conditions, with a temperature range of 15-20°C (60-70°F). 
  • High relative humidity, dew, and rain also contribute to the development of the disease. The ideal conditions for developing this disease are cool temperatures and high humidity, so controlling these factors can help prevent or slow the spread of the disease. 
  • For example, avoiding overhead irrigation and providing adequate air circulation can reduce humidity levels, while selecting maize varieties resistant to rust can also help reduce the impact of the disease.

Symptoms of Common Rust disease

  • The symptoms of Common Rust Disease of maize often appear after silking, when the maize plant is in its reproductive stage. 
  • The initial symptoms include tiny, chlorotic specks on the leaves. The formation of tiny, round elongated brown pustules on both the upper-lower surfaces of the leaves and other above-ground parts of the plant follows these. 
  • As the pustules mature, they change from brown to black and can cause the leaves to turn yellow and die early. 
  • Severe infections can reduce plant productivity and lodging, leading to yield losses. The most obvious sign of this disease is the golden-brown to black pustules on the plant’s above-ground parts. 
  • The release of urediniospores from the fungus Puccinia sorghi causes these pustules.

Common Rust disease management in Maize by cultural method

Cultural methods are a key component in managing Common Rust Disease in maize crops. Some of the strategies include:

  • Regular irrigation: Providing regular irrigation, particularly during flowering time, can help reduce the severity of the disease by decreasing the time that leaves are wet and promoting good air circulation in the crop.
  • Field sanitation: Maintaining good field sanitation practices is important for reducing the buildup of pathogens in the field. This can involve removing and destroying infected plant debris after harvest and avoiding planting maize in the same location year after year.
  • Crop rotation: Practicing crop rotation can help reduce the soil’s buildup of the pathogen. This involves growing maize in a different location each year and intercropping maize with other crops. This can help reduce the fungus’s potential to infect maize in subsequent years.

Common Rust disease management in Maize by biological method

  • Planting resistant maize hybrids and crop rotation can also help reduce the incidence of common rust. By alternating maize crops with non-host crops such as soybeans, wheat, or other grasses, the buildup of the rust pathogen can be reduced. 
  • Sanitation practices, such as removing crop debris, weeds, and infected plants, can also reduce the inoculum levels of the pathogen and help control the disease’s spread.
  • Foliar fungicides may also be used to manage common rust. Still, they should be used as a last resort due to the potential for fungicide resistance and negative environmental impacts.

Common Rust disease management in Maize by chemical method

  • Farmers can also control common rust by planting resistant hybrids by applying fungicides. 
  • Mancozeb and Dithane M-45 are two fungicides that can be used to treat maize affected by common rust. 
  • The fungicides should be applied as soon as the first symptoms of the disease are observed and repeated at 10-day intervals until flowering. 
  • The recommended application rate is 2.5g/liter for Mancozeb or 0.4% for Dithane M-45.

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Disease management in Maize by chemical method

Preventive measures for control of Common Rust disease

  • Plant-resistant varieties are available in your area.
  • Plant early to avoid ideal conditions for infection; use shorter-season varieties that mature sooner.
  • Check your crop for signs of disease regularly, especially during cloudy weather.
  • Use split nitrogen applications to ensure balanced fertilization.
  • Create a crop rotation that includes non-susceptible crops.

Conclusion

In conclusion, common rust caused by Puccinia sorghi is a significant disease affecting maize production. To minimize the intensity of the disease, it is recommended to plant resistant varieties. Other cultural practices, such as planting early, using shorter season varieties, monitoring crops regularly, ensuring balanced fertilization, and planning crop rotation with non-susceptible crops, can also help reduce the impact of common rust on maize production.

Last Updated:
Author: Reddy

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