Heat Sprouting

Tuber Internal Growth Defects: HEAT SPROUTING

Hair or spindle sprouting may occur in the field or in storage. It is associated with hot and dry conditions during late tuber growth (plateau stage). This disorder is also associated in seed from plants affected by psyllid yellows (caused by toxin injected by potato psyllid) and aster yellows (caused by mycoplasma injected by aster leafhopper).

External Appearance:

A small thin sprout grows prior to normal dormancy break.

Diagnostic Method:

External observation. Cut through eye to detect internal sprouting.

Internal Appearance:

Premature sprouting will cause a breakdown of starch to reducing sugars below the sprouted eye.

Cooking Appearance:

Chips and fries will have a brown irregular region along outer edge or end where the sprouted eye was.


Hot conditions late in the season will inhibit dormancy of mature tubers and push them to sprout. Experiments were reported that short exposure (few hours) to 100oF is able to induce heat sprouting of mature tubers. (This has been a concern with summer harvest in hot/dry States as Kansas.)

Control Measures:

  1. Plant deep.
  2. Avoid high setting varieties.

Tuber Internal Growth Defects: INTERNAL SPROUTING

Internal sprouting occurs in storage and is characterized by the sprout growing into the tuber, ingrowing. This can occur from a sprout from an eye on the underside of the tuber growing up and penetrating it or from deep eyes when the sprout grows sideways into the tuber. The tip of the internal sprout is commonly necrotic, brown. When it occurs, it usually is from an eye with multiple sprouts (rosette). This disorder occurs primarily with physiologically aged tubers and occurs when storage temperatures are above 55oF. The two major causes associated with internal sprouting are application of below effective levels of CIPC, a sprout inhibitor, and high pile pressure late in the storage season.