Gibberella stalk rot of corn
Gibberella stalk rot is caused by the fungus Gibberella zeae. Affected plants have shredded pith that is discolored a distinct pink or red and will die prematurely. Gibberella stalk rot causes dark streaks on the lower internodes. In moist conditions, round black specks may form at the lower nodes. These specks can be scratched off the stalk surface easily using a fingernail.
The fungus overwinters in corn residue and sometimes in seed. Spores are produced during wet weather. They are spread by wind and splashing water; infection takes place through the roots, wounds in the stalk, or leaf scars. Warm and wet conditions occurring two to three weeks after silking favor disease. This fungus also causes diseases of cereal crops, such as wheat scab.
Rotation and tillage will reduce inoculum. If more than 10 to 15 percent of stalks are observed to be rotted 40 to 60 days after pollination, the field should be scheduled for earliest possible harvest.
Gallery Images: G. Munkvold