A guide to late season corn stalk and ear rot diseases
Corn in parts of Nebraska has been damaged during recent weeks by hail and and stressed by very hot, dry conditions. These events and conditions can potentially lead to serious problems with grain quality during harvest and storage. Corn fields have sustained varying levels of damage. Plants that were impacted by hail likely have wounds on leaves, stalks, and ears where pathogens can infect the plant and cause diseases.
Some of these diseases and mycotoxins might have been exacerbated during the recent heat wave. The pathogens that cause stalk and ear rot diseases are common in fields and have probably already infected wounded plants. The severity of these diseases will depend on the extent of wounding and infection, as well as weather conditions and hybrid genetics.
As farmers approach harvest, the development and extent of these diseases should be determined in high risk fields so decisions can be made regarding field harvest order and how to best handle grain to minimize potential impacts of these diseases. Scouting is recommended prior to harvest to determine the extent of damage caused by stalk and ear rot diseases.
Stalk Rot Diseases
You can determine the risk for lodging and stalk rot disease incidence in fields using the “Push or Pinch Test.” While walking through fields, randomly select at least 100 plants that represent most of the field area and either:
- Push the plant tops approximately 30° from vertical . If plants fail to snap back to vertical, the stalk may have been compromised by stalk rot and is at risk for lodging prior to harvest.
- Pinch or squeeze the plants at one of the lowest internodes above the brace roots. If stalks crush easily by hand, their integrity has been reduced by stalk rots, making them more prone to lodging.
Fields with elevated risk for lodging should be harvested before less affected fields to minimize the chance of lodging and other complications during harvest.
Ear Rot Diseases
Ear rot pathogens will likely continue to grow during storage of infected grain and lead to grain mold that can seriously reduce grain quality and lead to major deductions at the elevator. Even under the best growing conditions, grain molds will usually continue to grow and, in some cases, may spread through the entire bin. Losses of up to 30% have been reported in south central Nebraska in recent years when grain was removed from storage, especially after a mild winter. Even during cold winters, remember that conditions inside the bin may be very different from its surroundings. Temperatures inside the bin may take several weeks to stabilize and condensation may develop, adding unwanted moisture that promotes fungal growth.