The Arthrinium phaeospermum is one of many species of dematiaceous anamorphs or dark pigmented fungi. It belongs to the family Apiosporaceae of the phylum Ascomycota. It is a very common saprobic mold that primarily affects plant life. It gets its much-needed nutrients from decaying organic material particularly from various species of vegetables, palms and grasses; for example, sweet potato, bamboo and sugar cane.

Previously, the species Arthrinium phaeospermum was known as Papularia sphaerosperma or Papularia sphaerosperma var. sanguinea. The use of Papularia has since been discontinued in favor of Arthrinium. Other known synonyms that reference the organism are Botryoconis sanguinea, Coniosporium onychophilum, Coniosporium phaeospermum, Gymnosporium phaeospermum, Melanconium sphaerospermum, and Stilbospora sphaerosperma.

Arthrinium phaeospermum is sometimes identified as the "bamboo black smudge" or the "sugar cane black smudge". It may be possible, however, for other species of plant-based fungi to cause familiar dark spots on bamboos and sugar cane plants that would be mistaken for Arthrinium phaeospermum. Only upon close inspection of the affected sample can the genus be accurately identified based upon the distinctive features of the organism's conidia.

Arthrinium phaeospermum is observed to be a multicellular and filamentous organism. The conidia of Arthrinium phaeospermum are dark-colored, usually brown, and lenticular in shape. It also has a faint crest around the middle of the structure. Furthermore, the conidia tend to develop in clusters. The colony will begin to appear as a white wool-like layer but will eventually reveal dark brown or black spots.

Traces of Arthrinium phaeospermum is most commonly found in soil and plant detritus. The colony grows quite rapidly covering the surface of the material with a wooly or cottony texture. Common hosts for the Arthrinium phaeospermum include wheatgrass, beachgrass, custard apple (atis), evergreen trees, various species of cane plants, peanuts, a number of flowering plants, oat-grass, various species of bamboo plants, wetland sedges, coconut palm trees, fruits belonging to the genus Citrus like oranges and lemons, sorghum, different kinds of tubers and many other grasses and plants. Certain kinds of beans, rice and cashews may contain low levels of the fungus.

Plants are not the only items that end up as suitable hosts for Arthrinium phaeospermum. Humans and animals may also be carriers of fungi. In almost all cases the human immune system are able to fend off infection. However, Arthrinium phaeospermum being a saprobic fungus is known to cause spoilage of various food products. The organism's conidia can be present in the air, both outdoors and indoors, although the latter scenario is less common. The species is also known to be unusually heat resistant for a conidiospore.

As such, if you leave a meal long enough on the dinner table, you will most likely have a plateful of Arthrinium phaeospermum among other nasty things. There are documented cases of acute food poisoning that are directly related to ingesting food items that are contaminated by Arthrinium phaeospermum.

It is quite probable that a person with a weak immune system may be susceptible to dermatological infections from a variant of Arthrinium. Common anti-fungal medications, particularly miconazole nitrate, may be effective to combat such infections.