Diplodia ear rot

Diplodia ear rot is a significant fungal disease affecting maize crops globally, caused by the pathogen Stenocarpella macrospora (previously known as Diplodia macrospora). This disease can cause severe damage in humid climates, leading to both quantity and quality reduction in corn production.

The primary host of this pathogen is corn. While it mainly affects ears, the fungus can also colonize stalks, leaf sheaths, and even leaves. The pathogen survives on infested crop debris, making it a persistent challenge in fields where corn is grown continuously without proper rotation.

Symptoms of the infection are quite distinctive: infected ears often appear shriveled and are covered by a dense, white to grayish mycelium growth. As the disease progresses, the grains become dull and discolored. A key diagnostic feature is the presence of numerous small, black, pinhead-sized structures known as pycnidia, which emerge on the surfaces of the husks and stalks.

The development and spread of Stenocarpella macrospora are heavily favored by high moisture conditions during the silking stage and throughout the grain-filling period. Temperature plays a secondary but crucial role, as warm weather combined with frequent precipitation creates optimal conditions for the dispersal of pycnidiospores via rain splash and wind.

Effective management requires an integrated approach to reduce the inoculum levels. Key strategies include:

• Rotating maize with non-host crops to allow residue breakdown.
• Selecting hybrids with good husk coverage to protect ears from pests.
• Implementing deep tillage to bury crop residues that harbor the fungus.
• Managing insect pests that create entry wounds for the pathogen.