Cladosporium fulvum, or Passalora fulva, is most identified with tomatoes. It belongs to the Cladosporium family, a species that thrive in temperate conditions; however, the high season for this fungi is during the later summer. It is found in compost, food, decaying wood, plants, soil and seeds. Its dry spores are airborne, making them easy to spread. The spores of Cladosporium fulvum can also be carried by water.

In the indoor environment, Cladosporium fulvum can be present in moist, porous surfaces as well as water-damaged materials. It can be isolated from condensation reservoirs and dirty refrigerators. Like other Cladosporium fungi, it can cause discoloration in paper and textiles. It has been identified as an allergen which is linked to Type I allergies such as asthma and hay fever. It may cause serious health conditions to people with weak immune systems, but it is most dangerous as a pathogen to tomatoes.