Considerations for Mouldy Corn
- Field to Bin

The upcoming corn harvest will prove interesting. A number of factors have come together through the latter part of the 2006 growing season which has resulted in a variety of moulds on the corn in certain fields. As a grower, you should scout your fields to evaluate the condition of you corn crop. Check all your fields and all the varieties that you planted. If you are a livestock producer you should have samples from questionable fields analyzed to determine the level of any toxins in the corn. Knowing the corn quality in each of your fields allows you to segregate your crop based on quality.

There is little you can do to prevent various moulds from infecting corn in the field. The proper drying of the corn and maintaining good storage conditions are important when these diseases are present.

Sanitation

Clean up any spilled grain in and around your grain storage system. By eliminating any residual grain material and fines, you may prevent yet another possible storage complication this fall and winter. There are always disease spores around grain drying systems.

Remove Fines

Fines and broken kernels in a bin are always a problem for airflow restrictions in a bin. This year, with the risk of moulds, there is even more reason to remove the fines before the corn gets to the bin. Set your combine to remove as much foreign material and fines as possible without causing excess grain damage. Damaged or broken kernels could provide more sites for disease infection.

Set the combine to blow out as many of the fines and eliminate as many of the small kernels as possible yet minimize kernel damage. Where possible, use screened sections on transfer augers to again remove fine material. If possible, use grain cleaners before the grain is put into the drier and before the dry grain is put into the bin. The fines and red dog contain higher levels of moulds than sound kernels. Dispose of corn screenings and do not feed to animals.

Figure 1: Rotary cleaners are one way of
removing fines in a grain handling system.

Drying Strategy

There are a few basics to follow to eliminate the continued growth of moulds in corn. One thing to remember in all this is the following; most mycotoxins are extremely stable molecules that can withstand drying temperatures and many industrial processes. Drying is not going to get rid of the continued growth of moulds or toxins but hopefully you can arrest any further development.

1. Dry corn that has been harvested within 48 hours.
2. Mould growth and mycotoxin production stops below 18% moisture content.
3. Dry the corn to under 15.5% moisture content.
4. Store dry corn below 5°C.
5. Do not use natural air or low temperature to dry mouldy corn.

Figure 2: Grain Bins

Coring the Bin

One way to reduce potential problems with fines is to core the bin. Coring a bin is a simple process of pulling a number of loads of grain out of a bin and putting them in a different bin or right back in the same bin. This operation breaks up the high-fines area in the centre of the bin. When this removed material is put back in a bin, the fines don't pack as tightly than if you did nothing. Ideally, these few loads should be put over a grain cleaner to remove the fines. If you have a grain cleaner - use it. Coring the bin will also establish the flow funnel. In simple terms, you get the grain flowing to the unloading grate.

Aerate Thoroughly, Aerate Often

Run the aeration fan for sufficient time to ensure that all the corn in a bin is at a uniform temperature. Areas of the bin that have poor airflow because of an accumulation of fines could cause problems. As the temperature in these pockets increases, the moulds could continue to grow and develop. Take good moisture samples and measure the temperature of the air exiting the bin when aerating. Run the fan until the exit air is the same a temperature as the ambient air temperature. Check your corn more frequently than other years. Problems will happen quickly and you need to stay on top of the situation. Use your nose to pick up any mouldy odours in the exhaust air from the bin. Our sense of smell can discern off-odours at very low levels.

Personal Safety

Farmers should be especially careful when handling corn with a known mould problem. The mould fungi, spores produced, associated dust, in addition to the toxins, can affect human health. Exposure to the spores of mould fungi could lead to acute or chronic allergic responses. Everyone working in or around mouldy grain should wear approved dust masks to minimize risks through the mouth and nose. These masks should be NIOSH approved: N95. As tested by the National Institute of Occupational Safety & Health, this quality of mask provides at least 95% filtration efficiency against solid and liquid aerosols that do not contain oil. Non-ventilated goggles will minimize exposure to your eyes.

Actions Required to Maintain Quality in Mouldy Corn

• Treat your good corn with kid gloves
• Leave fines and broken kernels in the field
• Clean corn going into the drier
• Dry wet corn quickly, natural air & low temperature drying not recommended
• Core the bin after filling
• Keep dry corn cold
• Check storage bins frequently
  

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