Tuber External Growth Defects: SWOLLEN LENTICELS

Lenticels are pores in the skin of tubers; botanically, they are stomates. They are involved in gas exchange of oxygen and carbon dioxide during respiration and photosynthesis. Besides giving an unmarketable appearance to the tuber, the major problem is that an entrance to pathogenic organisms, bacterial soft rot, pink rot and leak, is created.

Development and Appearance

Swollen lenticel scars in potatoSwollen or enlarged lenticels (water spot, water scab) develop when tissue below the lenticel swell and burst through the protective covering of the lenticel. This forms a corky mass around the lenticel. The disorder is somewhat reversible if the wet period is short.


This disorder is caused by exposure of the tuber to very wet conditions in the field or in storage. The swelling seems to be related to oxygen deprivation by the watery film covering the lenticel.


All varieties are susceptible.

Cultural Practices

Avoid over-watering. Avoid harvesting low, swampy spots in the field. Pick fields with good drainage. Avoid condensation in storage. Keep storage well ventilated.