Fusarium species exist as plant pathogens and are found on plant debris and in soil. Plant parasitic Fusarium causes wilting of many plants including crops such as tomatoes, bananas, sweet potatoes, pigeon peas, and pears. Some species of Fusarium are commonly isolated from seeds, especially those of cereals. Species of Fusarium also produce a number of different mycotoxins.

The Fusarium species are probably the most prevalent toxin-producing fungi in the northern temperate regions and are commonly found on cereals grown in the temperate regions of America, Europe and Asia. These toxins have been shown to cause a variety of toxic effects in both experimental animals and livestock and are also suspected of causing toxicity in humans.

In indoor environments Fusarium species are generally found under very wet conditions. They are commonly isolated from carpet and mattress dust, damp walls, wallpaper, polyester polyurethane foam, humidifier pans and areas where stagnant water occurs in HVAC systems. Some species cause keratitis in humans, and infect eyes and finger nails. Fusarium species are also an inhalation hazard.

Fusarium culmorum is born in soil and has a worldwide distribution. Indoors, it has been isolated from floor, carpet and mattress dust; damp wall and polyurethane foam. Fusarium culmorum is associated with allergy. It also produces vomitoxin, a trichothecene mycotoxin that causes a serious feed refusal and vomiting in animals fed contaminated feed.

Fusarium solani is a soil borne fungus found indoors in carpet and mattress dust; damp walls, wallpaper; polyester polyurethane foam; insulating cotton in duct liner; water pipes and humidifiers. Fusarium solani causes keratitis in humans. It is also associated with wounds and infections of the eyes and fingernails. It poses inhalation and deep skin (dermal) inoculation health risks to persons with weak immune systems. It also poses health risks related to major barrier breaks such as corneal perforation, major surgery, peritoneal or venous catheter presence, and injection drug use.

Fusarium verticillioides is soilborne. Indoors, it is found on humidifier pans and other areas where stagnant water occurs in HVAC systems. It is also found in mattress dust and on damp walls. Fusarium verticillioides causes keratitis in humans and invasive mycoses in immunocompromised people. It poses inhalation and deep skin (dermal) inoculation health risks to persons with weak immune systems. Fusarium verticillioides also poses the same health risks listed above under Fusarium solani.