Diplodia ear rot

Diplodia zeae (synonym Stenocarpella maydis) is a destructive fungal pathogen belonging to the Fungi kingdom. It is the primary causal agent of Diplodia ear rot and stalk rot in maize, posing a significant economic challenge to corn producers worldwide due to its impact on grain quality and overall crop yield.

The disease is characterized by the presence of white, dense fungal mycelium on the corn ear, which often starts from the base. As the infection progresses, the kernels become shriveled, and the entire ear may turn a dull brown or gray. Small, dark, pimple-like structures known as pycnidia develop on the ear, husks, and lower stalk internodes, acting as primary diagnostic markers.

The life cycle of Diplodia zeae revolves around overwintering on infested crop residues. In the spring, moisture stimulates the production of spores (conidia) within pycnidia, which are then disseminated by wind and splashing rain. The pathogen infects the plant through silk channels or wounds in the stalk tissue created by insects or mechanical damage.

Favorable conditions for the pathogen include high humidity and temperatures between 20°C and 30°C during the silking and grain-filling stages. High-density planting and reduced tillage practices contribute to the disease’s prevalence, as these factors provide a continuous reservoir of inoculum and maintain a humid microclimate within the corn canopy.

Management of Diplodia ear rot requires an integrated approach to minimize economic losses. Key strategies include practicing proper crop rotation to break the pathogen's life cycle, selecting hybrid varieties with tighter husks or known resistance, and utilizing effective residue management techniques such as deep plowing. Additionally, seed treatments are crucial to protect seedlings during the early stages of growth.