Common rust is a fungal disease that attacks cornfields across the United States. Specifically, it can be found in Midwest states like Illinois and Iowa. Caused by the fungus Puccinia sorghi, common rust can have a negative impact on yield if left to flourish.
- Symptoms: Initial symptoms of common rust include are chlorotic flecks, which develop into reddish-brown, oval-shaped pustules on top and bottom of leaf. Pustules are about 1/8 to 1/6 inch long. Leaves may become yellow and die.
- Geography: The disease can be found in cornfields across the United States, including Midwest states like Illinois and Iowa.
- Timing: Common rust typically starts showing up in June, but it can progress as corn matures.
- Conditions for development: The disease develops quickly in moist conditions with high humidity and consistent, cooler nighttime temperatures of 60 F to 75 F. Infection can occur with as little as 6 hours of leaf wetness.
- Scouting tips: Wind carries the fungus spores to Northern states from subtropical and tropical climates. Because spores are wind-blown, initial infection will be found in the top of the canopy. Secondary infections can occur every 7to 14 days as it spreads through the canopy of the crop. Scout weekly and check leaves for symptoms described above.
- Effect on yield: High levels of the disease can have a drastic, negative impact on yield. The fungus can weaken the corn stem, making it vulnerable to rot. Poorly filled kernels and lodging can occur.
- Management tips: Help your customers choose resistant corn varieties. Unfortunately, because common rust does not overwinter in the Midwest, crop rotation and tillage are not effective in preventing the disease. Recommend customers use a product such as Aproach® Prima fungicide proactively to prevent common rust. Aproach Prima contains two strong modes of action that effectively control corn diseases.
Aproach® Prima is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions.