- Hybrid susceptibility: Hybrids with low ratings of stalk strength or those that produce exceptionally large ears tend to be more prone to stalk rots [which can lead to lodging] than those with strong stalks and smaller ears.
- Carbohydrate stress: This can be caused by limiting photosynthetic ability, such as foliar diseases, insect damage, limited sunlight, high plant populations and nutrient or water deficiencies.
- Nutrient availability: Lack of certain nutrients can cause the stalk to cannibalize to get necessary nutrients to the ear, this leads to a hollow and weakened stalk.
- Diseases: Fusarium, Anthracnose and Diplodia are common stalk rots that lead to weakened stalks.
As a general rule of thumb, consider a fungicide application if a fungal disease is present on the third leaf below the ear leaf or higher on 50% of the plants at tasseling—which is when plants are most susceptible to disease, according to Iowa State University.
Recommendations vary, though, so talk to a local retailer, dealer or Extension agent to check thresholds. Be prepared to act quickly if needed.