Tipburn , is a calcium deficiency-related disorder associated with rapid plant growth, high relative humidity and excessive ammonium nitrate and potassium fertilization. Symptoms appear as brown to black necrotic areas of young developing leaves within and outside cabbage head. Maintain proper nitrogen and potassium fertilization and soil pH. Use a broadcast method for applying fertilizer rather than injecting fertilizer into row. Some tolerant cultivars are available. Hollow stem , is one of the greatest concerns of broccoli growers because fungi can enter the plant through the damaged openings.
Hollow stem is caused by rapid growth and boron deficiency.
Avoid varieties that tend to have hollow stem. Damping-off symptoms appear as brownish lesions on stems and roots. As the cabbage plant develops, the fungus causes a dark discolored area on the bottom of the cabbage head. Seed when soil temperature are favorable for germination and seedling emergence. Use disease-free transplants.