Causal Agent:
Physiological Disorder

Distribution:
Worldwide

Symptoms:
Hollow stem occurs in broccoli, cauliflower, and cabbage. The thick fleshy center (pith) of the stem or core splits due to an uneven growth rate with the rest of the plant. An elongated cavity is formed. The cavity may extend to either end of the plant to produce an opening to the outside environment. When such an opening does occur, infections by fungi and bacteria are common. 

Conditions for Disease Development:
Irregular or sudden rapid growth, high temperatures, high nitrogen levels and low plant populations favor development of this disorder. A boron deficient growing condition encourages hollow stem but is not a requirement.

Control:
Avoid excessive soil fertility. Increasing the planting density in broccoli reduces the incidence of hollow stem because the plant growth rate is decreased.