Molds that grow on fruit and other foods are tiny fungi that function as invasive species. Mold lands on the fruit and develops roots that bore down into fruit cells, which grow into spores that eventually become visible to the human eye. Moisture plays a role in attracting mold.
There are hundreds of thousands of mold fungi in the natural environment, and some of these molds are attracted to fruit. Mold that grows on hard fruits such as oranges, melons and grapefruit can be cut off of the fruit, leaving it edible. However, mold growing on soft fruits such as strawberries and peaches can easily penetrate the fruit's outer skin layer, causing damage inside the fruit. Moldy soft fruit must be discarded.
The longer fresh fruit is exposed to humidity or warm temperature, the more likely it is to become moldy. People should avoid bringing home fruits that may turn moldy by thoroughly checking fruits for bruising. They can also protect fresh fruits from mold by storing them in covered containers or plastic wrap. Refrigeration is another option as long as the refrigerator is clean and free of mold. Foods near the fruit must also be free of mold because it quickly spreads from one food source to another.