Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu; @Delmarplantdoc
With the recent stretch of hot, dry weather, many producers have begun to irrigate their sweet corn. Consequently, there have been reports of bacterial stalk rot in some areas where surface water or ponds have been used as water sources. Bacterial stalk rot, as the name implies, is caused by a bacterium that grows well on wet, decaying plant material. When water containing the bacterium is moved onto corn plants, particularly smaller plants in the vegetative stage, water containing the bacterium pools in the whorl and leaf sheaths and has easy access to natural openings or wounds on the corn plant. Once inside the plant, the bacterium can digest plant materials, and produce a slimy exudate that can clog water and nutrient conducting tissues. If infections are severe, a blight can occur. More often, we see an orange to brown, mushy rot near the shank or nodes randomly scattered on plants in the field. In addition, the rot has a characteristic, foul odor. Warm temperatures allow the bacterium to grow rapidly and produce more symptoms. This, in addition to the increased use of overhead irrigation when it is hot and dry, is why bacterial stalk rot tends to be an issue during this time of the year.
Bacterial stalk rot on corn is characterized by an orange to brown, slimy lesion and rot that gives off a characteristic odor.
Management
Managing bacterial stalk rot can be achieved by: 1) Incorporating residue into soil will reduce local inoculum that may spread to plants through rain splash; 2) using well water to irrigate fields instead of ponds or surface water; 3) using a hypochlorite system to treat water if you must use surface water for irrigation. An example of such a system is Accutab™; 4) utilizing drip irrigation instead of overhead irrigation, which may be practical for small operations; 5) applying more water less frequently, which may reduce the amount of overall plant wetness and reduce potential opportunities for infection. Copper fungicides will not help with disease management.