Diplodia Stalk Rot Figure 39. It overwinters as spores and pycnidia on corn residue and pycnidia or mycelium in seed. Pycnidia produce spores during wet weather, which are then spread by splashing water and wind.
Infections occur through the crown, roots, mesocotyl, and lower nodes.
Insects possibly carry the spores and introduce them into feeding wounds. The disease is favored by dry conditions early in the season followed by warm, wetter conditions after silking. In addition to the general symptoms on under Stalk Rots , Diplodia stalk rot can be identified by the development of numerous black pycnidia in the lower internodes of the stalk. Under very wet conditions, a white mold may develop on the stalk surface. Diplodia stalk rot sometimes is initiated at the ear shank when the ear also is rotted by D. maydis .