Causes of Stalk Rot: Several factors may contribute to stalk rot, including extreme weather conditions, inadequate fertilization, problems with nutrient uptake, insects, and diseases. This year, the combined effects of prevalent diseases such as northern corn leaf blight, southern rust, tar spot, and gray leaf spot may negatively affect stalk quality. However, the extent of the problem will depend on when these diseases develop and how badly the upper leaves of the plant are damaged.