Crazy top is an abnormal leaf mass that grows at the top of corn plants where the tassel should be. An uncommon corn disease, crazy top is caused by downy mildew fungus, and has been found in Midwestern fields. This soilborne fungus causes infection when young plants are subjected to saturated soil conditions or water accumulating in whorls or leaf sheaths.
The disease also brings about a deformation of plant tissues including excessive tillering, rolling of leaves and the proliferation of the tassel until it resembles a mass of leafy structures. Leaves of infected plants may be narrow and straplike in shape, leathery in texture and yellow or yellow striped in color.
“As far as management of crazy top corn goes, the number of things we can do is limited,” said Ben Jacob, Pioneer Field Agronomist. “We can look at improving drainage in that field, whether by adding tile or surface drainage. We can also look to control grass weed species, as they are alternative hosts for crazy top.”
Losses from crazy top are seldom severe enough in corn to warrant control.
Rotation to non-grass crops may help if drainage shows minimal results.