Diplodia stalk rot may first be evident when affected plants die suddenly during mid- to late-ear fill.
Upon examination, dark brown lesions can be found extending in either direction from the node.
Small black spots (pycnidia) may develop just beneath the stalk epidermis near the nodes. The black dots are not easily removed, which distinguishes Diplodia from Gibberella. (see images above)
Diplodia results in rotted stalks that are disintegrated and discolored (brown), allowing the stalk to be crushed or easily broken. (see images below)
Although the pith disintegrates, vascular bundles remain intact
Diplodia Stalk Rot Facts
Caused by Stenocarpella maydis fungus (formerly called Diplodia maydis)
Corn is the only host of this pathogen
Survives on corn stalk residues
Spores are spread by wind or splashing rain
Favored by warm, wet weather two to three weeks after pollination
Diplodia Stalk Rot Disease Cycle
Impact on Crop
Yield reduction
Kernel weight (test weight) may be reduced due to premature plant death
Potential harvest losses
Plant Lodging
Reduced grain quality if ears contact ground
Reduced harvest speed
Management
Genetic resistance – choose hybrids with high scores for stalk strength
Crop rotation – at least one year out of corn
Tillage to help break down crop residue
Maintain balanced fertility
Use moderate plant population if field has a history of stalk rot or lodging
Reduce plant stress if possible
Control stalk-boring insects to prevent wounds stalk rot organisms can enter.