Sections of corn stalk (above and below) showing diplodia stalk rot
symptoms. Note pycnidia on corn stalk node
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
Broken corn stalks due to Diplodia stalk rot infection (above and below).
The Diplodia fungus also causes kernel and ear rot in corn