Remove turtle and place in a quarantine tank. The infected areas should be cleaned and, if need be, affected scutes removed to ensure effective treatment underneath. Remove all squishy, off-white colored material. Be careful as the infection may have gone deep. Going too deep may cause you to penetrate into the body cavity. If you see that you will have to go more then a little bit past the surface of the shell, stop and seek veterinary assistance.
Listed below is a regimen that I have followed in treating shell problems and has yielded great results. Keep in mind that shell injuries will take months and sometimes years to get back to looking normal if the possibility exists. It takes weeks before the shell will look like it's getting better. While treating, you are not looking for signs of healing or repair - you are looking to ensure that it is not spreading.
Clean infected areas thoroughly with a strong, undiluted betadine, iodine or Nolvasan solution. Let the turtle air dry in a warm setting for about 45 minutes.
Apply a generous coating of Silvadene cream. Work into problem areas.
Leave the turtle dry and warm, ensuring that you do not over-heat, for 18-21 hours each day.
The next day, scrub entire shell with a one of the previously mentioned solutions, using a soft-bristled toothbrush
Place them into fresh, clean water. Let them swim, drink and eat for approximately 1 - 1 ½ hours.
Repeat procedure from Step 1.
This treatment performed daily or twice daily, depending on your time allocation, has been successful in as few as 8-10 days but in more extreme cases can take a few weeks. It is difficult to tell success right away, so it is often discouraging. It is, however, quite effective and you will begin to see small improvement (in most cases) in only a few weeks.
NOTE: The betadine bath's 'weak tea' solution is not advised as this can potentially bring about health issues later on.
The most common causes of this condition are water quality and injuries, albeit minor at times, from habitat decorations (scratched while climbing, swimming or diving into the water, substrate, heater burns, etc). It appears most times as white patches on shell.
