What Causes Mold to Grow on a Clementine?

Under certain conditions, the bag of fresh clementines you brought home from the market can start to grow visible mold in a matter of days. Mold spores are found in both indoor and outdoor locations, making it important to understand what causes molds to grow on clementines. Understanding the causes of mold, as well as the ideal growing conditions that can lead to rapid mold growth, can help you to make sure your clementines stay fresh and appealing for as long as possible.

Sources of Mold

Mold spores can be found both indoors and outdoors. These spores, which are what certain types of fungus use to reproduce, are often airborne. They may also be found on the surface of foods, plants or in soil. If the cardboard boxes that fruits are shipped in become damp during transit, they can also develop mold growth. Farms are often another major source of mold, meaning the spores may already be on your clementines when they reach the supermarket.

Environmental Factors

Mold counts tend to peak in the afternoon, unlike pollen, which peaks in the morning. Mold can grow when given any sort of organic material to eat, whether it is paper or citrus fruit. Condensation can also give the mold spores on the surface of a clementine the added boost of moisture they need to grow larger. Indoor mold levels can spike if your home is not regularly cleaned, as this gives the mold time to increase in size.

Ideal Mold Growing Conditions

Mold thrives best in warm, humid conditions -- in areas of your home where humidity is over 60 percent, or where temperatures are consistently between 70 and 100 degrees F. This problem can be exacerbated by poor air circulation, so having a breeze can help to prevent or slow mold growth. However, it is worth noting that mold counts can be higher in homes where celling fans are used instead of air conditioning, as air conditioners help to reduce humidity.

Citrus-specific Molds

Certain types of molds that may be in your home may target clementines and other citrus fruits. Among these are penicillium italicum and penicillium digitatum, which can cause soft spots on the rinds of a clementine, and is usually blue or green in color. Sooty mold is another type of mold that can grow on citrus. Unlike penicillium molds, this mold grows only on the surface of fruit, and can be rubbed away. It is often caused by small insects excreting a sweet waste that mold thrives upon. Septoria rot can also affect clementines during a patch of wet weather, causing brownish spots along the surface of the fruit.