Corn Plant Blight

Blight

• Blight is a collective term for a range of fungal disease that can affect almost any type of plant. Specifically with regards to corn, northern leaf blight, bacterial leaf blight, anthracnose leaf blight and southern leaf blight are major diseases. Each disease is caused by a different fungal disease agent and characterized by different symptoms. Symptom identification is essential to identifying the fungal pathogen causing the disease and thus treating the disease.

Symptoms

• Anthracnose leaf blight is caused by the fungus Colletotrichum graminicola and its symptoms include small, water-soaked lesions on corn leaves and diminished new growth. The disease agent of northern corn leaf blight is Exserohilum turcicum; infected corn will break out in long, green to brown spindle-shaped lesions and death of signification amounts of the corn plant's foliage. Bacterial leaf blight is caused by Pseudomonas avenae; leaves infected with this disease show dead striped and spots up and down corn leaves. Finally, southern leaf blight, caused by Bipolaris maydis, shows similar symptoms to northern corn leaf blight, though the leaf lesions tend to be much smaller than those of northern leaf blight.

Natural & Preventative Controls

• Corn cultivars vary in their resistance to blight diseases, so if blight has been a problem on corn plants in the past, consider purchasing a more disease-resistant cultivar. Bacterial leaf blight usually dies off on its own as the corn tassels, so treatment is not always necessary, though effective control has been shown to reduce the instance of bacterial leaf blight. Both northern and southern corn blight are more common after periods of prolonged leaf wetness, so always water your corn plants early in the day to give them a chance to dry off in the sunlight.

Chemical Controls

• The University of Florida Extension recommends a combination of sterol-inhibitor and strobilurin fungicides and "protectant" contact fungicides for control of both northern and southern corn leaf blight. With these two exceptions, cultural practices are generally much more effective at controlling the spread of disease than are fungicides, so fungicide treatments are not recommended for corn plants infected with bacterial leaf blight or anthracnose leaf blight.