Crazy top is a result of a soil borne pathogen that can affect corn plants in the United States and Canada. The very excessive twisting, tillering, and rollin of upper leaves appear first and then the very leafy tassel comes when the tassel is produced. Resulting in the tassel to have a bushy look to it. As the plant grows the internodes become shortened or elongated, a high number of ear shoots will also become present, along with leaves that are long and narrow. Pollen will not be produced, leaves can have yellow stripes but not in all cases and stunting of the corn plant may also occur.
Since crazy top is a soil borne pathogen and overwinters in the soil as oospores. During periods of heavy rain that may cause prolonged flooding or ponding (24-48 hours) during the early growth stages is when infection can occur. The oospores germinate in the water and become zoospores which then use water to swim in and infect the growing point of the young corn plant. Other plants that can be affected are small grains, grasses and sorghum.
There is no control warranted for crazy top but there are a few things you can do to minimize crazy top in your fields.
- Proper soil drainage, attempting to avoid prolonged periods with standing water.
- Manually removing crazy top infected plants within your field.
- Controlling grass weeds to help reduce the inoculum sources.