Excessive tillering, rolling, and twisting of the upper leaves appears first. The tassel and ears may be replaced by a massive leafy structure described as “crazy top.” The disease occurs in low, wet areas of the field that remain saturated for an extended period of time from planting to the four- to five-leaf stage. Improve soil drainage or avoid planting in low, wet spots.
Taken from Corn Production Handbook, KSU Extension
Pest photo source
Diagnosing Corn Problems in Kansas, KSU Extension