Fluctuations in soil moisture and high soil temperatures often lead to growth cracks and malformation

Growth Cracks - The photograph above shows the extent and depth of growth cracks. Such cracking is related to uneven soil moisture availability and rapid water uptake resulting in large charges in tuber moisture content and growth rate. Dry periods or periods of high temperature followed by rains can also cause growth cracks.

Malformation - Malformations result from secondary growth following a cessation or inhibition of normal growth. The type and severity of the defomration is influenced in part by the stage of tuber development at which growth is interrupted. High temperatures, even when adequate soil moisture is present, has been shown to result in malformations. Growth after stress periods slow or stop tuber growth may occur only in certain areas of the tuber, resulting in malformation.

Prevention of growth cracks and malformations:

To prevent growth cracks and malformations, gardeners should ensure potatoes are planted at the proper spacing in well-drained soil and kept uniformly moist, but not saturated, during the growing season. Covering the soil with 2 to 4 inches of a loose mulch will help keep the soil moist and prevent extreme fluctuations in temperature. Excess amounts of fertilizer or manures should be avoided.

Hollow Heart

‘Hollow Heart', as seen above, results when tubers grow too fast; the inner tissue of the tuber pulls apart resulting in a void inside the tuber. In this instance, the hollow heart defect extended all the way to the surface. Too much nitrogen, too much water, too high a soil temperature or having too much space between plants all contribute to these problems.

Pink Eye

In the above photo there is a light discoloration within the skin tissue. This usually can be related back to pinkeye. There also is a granular, brown, discoloration around the hollow heart lesion. This discoloration is typical of pinkeye. In addition, the vascular tissue is exhibiting a brown discoloration also, is typical of a pinkeye infection or Verticillium wilt (which is associated with pinkeye). When the crop is stressed, pinkeye tends to show up ¹

According to Stephenson, et al., the orgainism causing pink eye is unknown. Pink eye symptoms however, has been related to bacterisa as well as fungal pathogens. Verticillium has been shown to be associated with pink eye.

Additional Information:

"Irish" potatoes (Solanum tuberosum L.), harvested for storage, should be dug after vines are killed by the first fall frost. This is especially important for potatoes intended for long-term storage; in addition, the vines should have been dead for at least ten to fourteen days before the tubers are dug and stored. Potatoes harvested too early easily `skin' during the harvesting and handling period and do not store well.

References used:

¹ Marleen Clark, Plant Health Research & Diagnostics, PEI Department of Agriculture & Forestry, P.O. Box 306, Kensington, Prince Edward Island, CANADA C0B 1M0 (personal communication)

Rowe, R.C., ed. 1993. Potato Health Management. American Phytopathological Society. St. Paul, Mn.

Wtevenson, W.R., Loria, R., Franc, G.D., Weingartner, D.P. 2001. Compendium of Potato Diseases; Second Edition. American Phytopathological Society. St. Paul, Mn.