Fumonisins are naturally occurring mycotoxins found mostly in cereal grains, mainly corn. Fumonisins are a more recent discovery compared to aflatoxin and DON. Fumonisins are produced by several fungi of the Fusarium genus. The fumonisin family consists of fumonisin B1, fumonisin B2 and fumonisin B3. Fumonisin B1 is the most abundant, accounting for about 70 to 80% of total fumonisins. The main concern with fumonisins are feed contamination that can have detrimental effects, particularly to horses and pigs. Fungal and fumonisin formation occurs mainly before harvest. Insects play an important role in fumonisin contamination since they act as a wounding agent. Temperature and rainfall conditions are related to fungal growth and fumonisin contamination. In general, fumonisin contamination is related to plant stress, insect damage, drought and soil moisture. In 2001 FDA issued guidance levels for fumonisins in corn-based foods and feed to reduce human and animal exposure. FDA advisory levels are shown below.