Mycotoxins are toxic biochemical substances produced by fungi. They are produced on grains, fishmeal, peanuts, and many other substances, including all kinds of decaying vegetation. Mycotoxins are produced by several species of fungi—especially Aspergillus, Penicillium, and Fusarium—under appropriate environmental conditions of temperature, moisture, and oxygen on crops in the field or in storage bins. In recent years, research on this subject has indicated considerable specialization in mycotoxin production by fungi. For example, aflatoxins B₁, B₂, G₁, and G₂ are relatively similar mycotoxins produced by the fungus Aspergillus flavus under conditions of temperatures ranging from 80-100°F (27-38°C) and 18-20% moisture in the grain. Aflatoxins are among the most potent carcinogens among naturally occurring products. Head scab on wheat in the field is produced by the fungus Fusarium graminearum which produces a mycotoxin known as DON (deoxynivalenol), also known as Vomitoxin.