September 28, 2007

Aspergillus ear rot that can lead to aflatoxin accumulation.

A few loads of corn harvested recently in Cass, Johnson, and Nemaha counties were rejected at elevators last week because of positive results from black-light screening. That test is a presumptive positive for aflatoxin. Additionally, staff at the Federal Grain Inspection Service laboratory reported that some specimens received there had aflatoxin concentrations exceeding FDA action levels. Presently, it is too early in the harvest to know the extent and levels of aflatoxin contamination in this year's corn crop, but people selling and buying corn should be aware of the situation and take action, if necessary, to protect themselves against aflatoxin contamination.

Aflatoxin is a mycotoxin produced by fungi in the genus Aspergillus, most commonly A. flavus. This fungus is commonly present in the soil and can cause ear rot diseases under certain conditions. The fungus causing Aspergillus ear rot of corn produces copious amounts of greenish-yellow spores (Figure 1), particularly on damaged kernels. The presence of the fungus in kernels does not correlate with the presence of aflatoxin, nor does the absence of visible fungal growth correlate with the absence of aflatoxin.

Drought and high temperatures tend to favor the production of aflatoxin in corn. Portions of southeast Nebraska missed some late-season rain events received by much of the rest of the state. Irrigation is not as common in fields in eastern counties, thus crops rely solely on rainfall for moisture and are at higher risk for drought stress. This may be to blame for the aflatoxin in this area this year.

For more information

Market Journal
Market Journal interview with author Tamra Jackson on potential aflatoxin probems.

NebGuides

(2012 Note: These NebGuides are no longer available.)

• Understanding Fungal (Mold) Toxins (Mycotoxins), G1513
• Use of Feed Contaminated with Fungal (Mold) Toxins (Mycotoxins), G1514
• Sampling and Analyzing Feed for Fungal (Mold) Toxins (Mycotoxins), G1515

  Michael Carlson
  UNL Diagnostic Toxicologist/Analytical Chemist
  Tamra A. Jackson
  UNL Extension Plant Pathologist