Aflatoxins are potent, naturally occurring toxins that sometimes develop in corn and certain other crops. 

Aflatoxins are also among the most carcinogenic substances known.

There are well-defined limits on how much aflatoxin is allowable in corn, based on the intended end use. For example, corn intended for human consumption must have less than 20 ppb (parts-per-billion!). 

More information on aflatoxin can be found in the UK Extension publication, Aflatoxins in Corn, ID-59, at http://bulletin.ipm.illinois.edu/article.php?id=1244.

The prevalence of drought conditions this growing season may result in aflatoxin contamination, at least sporadically. Some agents have expressed interest in informally scouting for the problem in advance of harvest. 

This is an excellent idea. The problem is, it is very difficult to assess standing corn crops for aflatoxin contamination. Some of the reasons for this include:

• The mold associated with aflatoxin may not always be visible in contaminated grain.

• The presence of the mold does not mean aflatoxin is present.

• There are several green molds on corn, and they can be hard to tell apart.

• Even when it occurs, aflatoxin contamination is very sporadic for lots of reasons, so a grower may have very high levels in one field and low levels in another. 

Having now lowered expectations, I do think scouting is a good idea, especially this year. It might help producers manage their risks a little more wisely. 

The scouting approach that makes the most sense to me is to visually inspect the ears for mold typical of Aspergillus ear rot. Scouting can be done any time after black layer.