Southern Corn Leaf Blight

Family: Pleosporaceae

About Southern Corn Leaf Blight

Life Cycle

Southern corn leaf blight is caused by the fungus Bipolaris maydis, which primarily follows an asexual disease cycle. Under the right conditions, conidia (asexual spores) are released from wounds of a diseased corn plant and dispersed to surrounding plants through splashing rain or wind. After conidia are transmitted from an infected plant to a healthy one, the fungi germinate on the leaf’s tissue. Once infected, leaf tissue will turn brown and eventually the leaf will fall. In good conditions, spores can germinate and penetrate the plant in just 6 hours. Bipolaris maydis overwinters in plant debris as spores until favorable conditions return. This fungus is also capable of following a sexual disease cycle, but this has only been found in laboratory environments.

Southern Corn Leaf Blight Identification and Habitat

Identification

Once infected, host plants will develop small, diamond-shaped lesions on their surface. Lesions are tan in color with brownish borders. With age, these lesions will stretch out and appear longer. Lesions may combine together causing large portions of leaf tissue to be burned. In the T strain of the disease, lesions are more ovular and larger in size compared to those of the O strain. Typically lesions will appear on leaves near the base of the plant before other parts of the canopy.

Varieties

• • Race O
• • Race T
• • Race C

Habitat

This disease favors warm and moist conditions for development. Temperatures ranging between 70 and 90°F are ideal for the fungus to survive and germinate. Extended wet conditions are important for fungi to be able to germinate quickly and effectively. Highly dense corn crops with minimum tillage are good for spread of disease as spores can easily be splashed or blown from one plant to another.

Southern corn leaf blight Management and Control Methods

Cultural Control

The most effective way of reducing chances of infection is by planting hybrid species of corn. Hybrid species will greatly reduce chances of infection as they are bred to be resistant to the disease. Tilling fields at the end of the season is very helpful because it will break down the infected plant residue left from diseased plants, reducing chances of spores germinating next season. Crop rotation is also recommended to reduce chances of further infection when economically viable.

Chemical Control

Foliar fungicides can be a helpful deterrent in seed production fields. Before using fungicides, always check the label for cautionary advice and application guidelines.

Alternative Southern Corn Leaf Blight Names

• • Maydis Leaf Blight

Sources