NPIPM:Crazy top on Corn
Authors: Byamukama, E., Yabwalo, D., and Ali, S.
Causal Organism
Crazy top is caused by a fungal pathogen Sclerophthora macrospora (Synonym: Sclerophthora/Phytophthora macrospora).
Symptoms and Signs
Crazy top symptoms vary with time of infection and the extent of systemic colonization. The main symptoms include distortion of the plant through excessive tillering, and proliferation of the tassel, where the tassel may have a mass of leafy structures. Infected plants may be stunted. Other parts of the plant like the ear may also have excessive leaf like structures. Leaves of infected plants are narrow and leathery and may have long yellow stripes. The tassels of infected plants do not produce pollen.
Disease Impacts
Crazy top is usually found in a few corn rows near the edge of the field or low spot areas. It is not wide spread within the field therefore its impact on grain yield is limited.
Life Cycle and Epidemiology
The crazy top pathogen survives in the soil as hardened spores called oospores. When the soil has excessive moisture (mainly after flooding), the oospores germinate and produce another type of spores called zoospores. These swim in water are attracted to young corn seedling plants and infect young leaf tissue. The infection is systemic and fungus can be found in foliar parts of the plants including the tassel. The ear is usually not present because the fungus interferes with hormonal balance. Intense rain, ponding, and prolonged flooding increase the risk for crazy top disease. Wild grasses are also hosts for the craze top pathogen, the reason infected corn plants can be found at the edge of a corn field.
Management Approaches
• Improve drainage to reduce chances of ponding or flooding
• Manage grassy weeds to reduce inoculum build up
Other Online Resources
Sweets, L. 2011. Crazy top of corn. https://ipm.missouri.edu/ipcm/2011/5/Crazy-Top-of-Corn/
Crop Protection Network. Crazy top of corn. https://cropprotectionnetwork.org/encyclopedia/corn-disease-management/foliar-diseases/crazy-top/
