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
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.
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.
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.