Brown rust, also known as “leaf rust,” is a fungal disease that affects wheat plants. It causes small, round-oval spots on the leaves, sheath, and stem. These spots are called pustules and are bright orange. The disease spreads quickly in warm and humid conditions and can severely impact the plant’s health.
If the attack is severe, the plant may mature early, have poor root development, and produce light and shriveled grains. Leaf rust is among the most widespread and damaging wheat diseases in many areas. Wheat is a staple food crop that provides a significant portion of the world’s caloric intake. To attain and ensure a high wheat crop yield, it is essential to understand and prevent diseases that can negatively impact its growth and production.
Brown Rust disease management in Wheat
The causal organism of Brown Rust disease
Puccinia recondita tritici is a fungus that causes this brown rust disease of Wheat. Yellow rust disease thrives under conditions of low temperature and heavy humidity. As a result, yellow rust sickness is possible throughout January and February. This illness is more likely to spread in cold and humid climates.
Disease cycle of Brown Rust disease
- Puccinia recondita tritici requires living green plant material to survive.
- It overwinters as dormant mycelium or active sporulating lesions on volunteers or early autumn-sown crops.
- The fungus can survive low temperatures within plant tissue.
- It grows in cool and moist weather in the spring and produces active sporulating lesions.
- Optimal conditions for spore germination, penetration, and new fragment production are 10-15°C and 100% relative humidity.
- Temperatures over 20°C inhibit the fungus, but strains tolerant of high temperatures exist.
- The complete cycle from infection to new fragment production can take as little as seven days in ideal conditions and may be repeated many times in one season.
- Dark teliospores may be produced during late summer, but their function in the disease cycle is unclear.
- Teliospores may contribute to the development of new races through sexual recombination.
Favorable conditions for the spread of Brown Rust disease
- Optimal growth occurs at temperatures between 15-22°C, with free water. Dry and windy conditions can promote the spread of disease, making it difficult to control.
- Late nitrogen applications can also increase the severity of the infection. The fungus is killed at temperatures below five °C and inhibited at temperatures above 25°C, so hot summers and cold winters can reduce its spread.
- The disease has a 7-day optimum cycle in mid to late summer, making it most active during these times. Brown rust is most prevalent in coastal regions with frequent mists, particularly in southern counties.
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