How long does it take for mold to appear on an object?
There are a lot of variables including climate, temperature, air supply, humidity and air movement. I've had mold appear in a coffee cup over night in humid areas open to the outside. Northern areas with lower temperatures are less likely then hot and humid areas in the south.
Several factors affect how long it takes apple sauce to mold. The more sugar it has, the longer it will take. Also, apple sauce that is kept at room temperature will mold much more quickly than apple sauce that is kept in the refrigerator. Generally speaking, apple sauce will get mold on it after one to two weeks.
It would take a longer time to grow mold on an orange in the fridge than it would being left out in room temperature. Putting fruit in the fridge helps the fruit stay fresher for a long time period. I would think it would take a couple of weeks, in other words a long time for an orange to grow mold while in the fridge.