The four main types of bruises are:
Skinning or Feathering
The skin is rubbed off during handling. This usually affects immature potato tubers that have not yet been cured. Exposed areas are more sensitive to wind, sunshine and dry air.
A stereotypical bruise; this occurs when the tuber impacts a solid object causing damage to the cells in the tissue without breaking the skin. Signs are visible 24-48 hours later under the skin. Crop usually appears normal, but will show darkened area(s) when cut into. Appears like a human tissue hematoma.
Caused by an impact with a solid object which pierces the skin. Diseases are easily able to invade crops with shatter bruises. Crop shows a split. Differs from fruit splitting when growing as the bruise edges are normally softened and curved inwards rather than appearing as a tightening of the skin.
Usually develops in storage, but may also occur when the tuber/fruit/bulb is still growing and is impeded by solid soil or rocks. Often results from dehydration from low soil-moisture before harvest or poor humidification in storage. Crop may feel softer.
None, use immediately.
Handle crop carefully at every stage in the process. Do not plant damaged bulbs/tubers. Be careful when harvesting as tools and equipment can easily damage crops. Inspect crop before storing and store in correct conditions.