November 1, 2022
Crazy top in corn is a common occurrence across the United States in areas where prolonged periods of rainfall causes flooding in fields after planting. Symptoms can be seen during the vegetative stage of growth; however, they are most noticeable at tasseling. At tasseling, the plant produces a leafy structure resembling rolled up corn leaves instead of the tassel (Figure 1). Early plant symptoms can include shortening of the plant, increased tillering, and twisted leaves which is usually a result of infection at the ear nodes.
Figure 1. Leafy growth that replaces the tassel in crazy top.
Infection occurs early in the plant’s life cycle when the plant is vulnerable to flooding, from emergence up to V4 or V5. During this time water moves the pathogen, Sclerophthora macrospora, into the whorl of the plant causing infection. The crazy top pathogen overwinters as an oospore and is easily moved during times of soil saturation which leads to infection.
When considering management for crazy top, there aren’t many available options. The best option is field drainage. Having a drainage system that can quickly remove water is the best way to help mitigate the risk of crazy top infection.
Sources
Crazy top of corn. 2022. Crop Protection Network. https://cropprotectionnetwork.org/encyclopedia/crazy-top-of-corn#:~:text=Crazy%20top%20is%20caused%20by,lends%20this%20disease%20its%20name/.
Iriarte, F. and Robertson, A. 2009. Signs of crazy top in corn. Integrated Crop Management. Iowa State Extension. https://crops.extension.iastate.edu/cropnews/2009/07/signs-crazy-top-corn/.
Strunk, C. (originally Byamukama, E.) 2022. Crazy top disease developing in corn. South Dakota State University Extension. https://extension.sdstate.edu/crazy-top-disease-developing-corn/.
Web sites verified 9/25/22.
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