Are there any gall-like structures that have replaced bluestem seeds?
Are the entire inflorescences converted into galls with fungal spores?
Do the leaves have spots or blotches?
Are there any rust-colored spots on foliage?
Do the flowering heads have viscous, creamy-pink exudations, hard brown spiky structures (sclerotia) are formed subsequently?
Kernel smut caused by Sphacelotheca occidentalisis is characterized by gall-like structures that replace bluestem seeds. Cultural practices are the primary means of managing kernel smut. If the infection is mild, cut off and destroy all infected leaves. Avoid excessive rates of nitrogen fertilizer. Plant only certified seed.
Culm smut caused by Sorosporium provinciale converts entire inflorescences into galls containing teliospores. If the infection is mild, cut off and destroy all infected leaves. In more severe infections all you can do is destroy plants to stop smut from spreading.
Your plant is suffering from a fungal leaf spot. These can come from several fungus diseases, causing spots to occur on foliage. Spots may enlarge rapidly, especially in wet weather. Destroy infected leaves or plants. Spray plants with sulfur to prevent the disease from spreading, especially if the weather is wet. Spray between rains. Prevent problems by thinning plants to provide good air circulation.
Rust-colored spots on foliage indicate a fungal disease - Rust. Provide good air circulation around plants by thining them. Avoid making leaves wet when watering. All infected leaves should be removed. Spray leaves with sulfur early in the season to prevent rust or to treat mild infections.
Ergot is a fungal disease of inflorescences. Ergot constitutes a health hazard to humans and animals that consume it. Remove and destroy all infected inflorescences as soon as the symptoms are seen. Avoidance of ergot is achieved through the selection of cultivars that flower during periods of dry weather.
One of the most serious pests of big bluestem is the bluestem seed midge - Contarinia wattsi. This insect pest can reduce seed yields by over 50%. There is no control, however, a wasp Tetrastiches nebraskensis parasitizes the midge in the Midwest.
https://plants.usda.gov/pmpubs/pdf/gapmcarbigblue.pdf
https://www2.ipm.ucanr.edu/agriculture/rice/Kernel-Smut/
Ellis, B. W., Bradley, F. M., & Atthowe, H. (1996). The Organic gardener's handbook of natural insect and disease control: a complete problem-solving guide to keeping your garden & yard healthy without chemicals. Emmaus, Pa.: Rodale Press.
Sreten null
Hi! I’m Sreten Filipović. I graduated from the Faculty of Agriculture at the University of Belgrade, with a master's degree in Environmental Protection in Agricultural Systems. I’ve worked as a researcher at Finland's Natural Resources Institute (LUKE) on a project aimed at adapting south-western Finland to drought episodes. I founded a consulting agency in the field of environment and agriculture to help farmers who want to implement the principles of sustainability on their farms. I’m also a founding member of the nonprofit organization Ecogenesis from Belgrade whose main goal is non-formal education on the environment and ecology. In my spare time, I like to write blog posts about sustainability, the environment, animal farming, horticulture, and plant protection. I’ve also published several science-fiction short stories.
You can find me on LinkedIn at https://www.linkedin.com/in/sreten-filipovi%C4%87-515aa5158/
