Fields of corn stretching toward the horizon are a familiar sight, symbolizing agricultural abundance. Yet within this familiar landscape, a peculiar phenomenon can occur that disrupts the expected uniformity: the crazy top.
Understanding Crazy Top Disease
Crazy top is a disease that affects corn plants during their early growth stages, primarily caused by the soil-borne fungus *Sclerophthora macrospora*. This pathogen thrives in cool, wet conditions, often appearing in low-lying areas of a field where water tends to accumulate. The disease name is derived from the distinct and bizarre symptoms it produces on the plant's leaves and tassel.
How the Pathogen Infects the Crop
The infection process begins when fungal spores, resting in the soil, are splashed onto the lower leaves of a young corn plant. Germination occurs rapidly when temperatures are between 60°F and 70°F with consistent moisture. From the leaf, the fungus moves systemically into the vascular system of the plant, traveling upward to the growing point. This systemic invasion is what leads to the severe distortion observed later in the season.
Visual Symptoms to Identify
Identifying crazy top is relatively straightforward once you know what to look for. The most characteristic symptom is the proliferation of leafy growth on the ear shank and ear tip, which replaces the normal development of the ear. Leaves may become stiff, twisted, and display a pale green or yellowish color. The most dramatic visual cue is the formation of structures that resemble a cauliflower head or a mass of small, leafy tufts where the tassel should be.
Environmental Triggers and Risk Factors
While the fungus is always present in many soils, the disease requires specific environmental conditions to become a significant problem. Cool temperatures combined with saturated soil are the primary triggers. Planting dates that place the crop in its most vulnerable stage during periods of cool, rainy weather increase the likelihood of an outbreak. Fields with poor drainage are consistently at a higher risk than well-drained sites.
Management and Control Strategies Because the fungus is soil-borne and systemic, controlling crazy top once a plant is infected is impossible. Management relies entirely on proactive strategies implemented before or at planting. The most effective cultural practice is to ensure excellent field drainage through proper grading or tile installation. Planting later in the season, when soil temperatures are warmer, can help the crop avoid the cool, wet window when the fungus is most active. Impact on Yield and Economic Concern
Because the fungus is soil-borne and systemic, controlling crazy top once a plant is infected is impossible. Management relies entirely on proactive strategies implemented before or at planting. The most effective cultural practice is to ensure excellent field drainage through proper grading or tile installation. Planting later in the season, when soil temperatures are warmer, can help the crop avoid the cool, wet window when the fungus is most active.
The financial impact of crazy top is directly related to the severity of the outbreak. Plants infected early often fail to produce a harvestable ear, leading to a significant reduction in yield potential. While not typically a disease that kills the plant outright, the distortion of the ear shank prevents kernels from forming. In fields with severe infection, the economic loss can be substantial, making accurate diagnosis and preventative planning critical for growers.
