Aflatoxin in Corn

Monday, September 8, 2014

Aflatoxin in corn has been a problem in the past. In scouting fields in the area, I have found some ears with what appears to be aspergillius fungus on the tips of the ear. I did not see much evidence of earworm damage in those fields. The fungus was primarily showing up on the tips of ears that had grown past the end of the shucks. At this point in time the amount of aspergillius does not seem to be a problem.

Aspergillius flavus and aspergillius parasiticus are the two fungi that can infect corn kernels in the field and in storage. The fungus is identified by its color with aspergillius flavus being yellow-green and aspergillius parasiticus being a gray-green. The fungi overwinter on plant residue. The spores are dispersed by wind and land on silks and kernels. Under favorable environmental and crop conditions, the spores will begin to grow. Wounds from insect feeding create favorable growth sites.

Hot, dry days and warm nights combined with moisture content levels of 17 to 30 percent, are favorable for aspergillius development on the kernels. Under stress, the fungi can initiate aflatoxin production on infected kernels of susceptible hybrids. The most common stresses leading to aflatoxin production in the field include excessive heat and drought stress. Poor conditioning and storage conditions, such as insufficient drying and improper storage of wet grains, can lead to post-harvest infection and aflatoxin production on infected grain. There are some steps to mange harvest that should help reduce the risk of potential problems from aflatoxin :

1. Scout fields for insect damage to ears and aspergillius infection at black layer and two weeks prior to harvest.

2. Fields showing ear rot or insect damage should be harvested as soon as possible.

3. Combines should be adjusted to reduce kernel damage. Opening sieves and increasing fan speed may help remove damaged or light weight kernels.

4. Dry corn immediately to 12.5 to 13.0 percent moisture. Cool the grain quickly. Minimize kernel cracking and other damage.

5. Grain should not be harvested at rates that exceed drying capacity.

Harvest is just beginning in the area and local elevators will be monitoring for aflatoxin. Depending on the weather and harvest progress, aflatoxin may not be a problem but conditions need to be monitored as the harvest progresses.