Gibberella and Fusarium Ear Moulds

The most common and important ear mould in Ontario is Gibberella zeae which is the sexual reproductive stage of Fusarium graminearium. This fungus not only infects corn but also small grains such as wheat. Although, the fungus can produce a white colour mould which makes it difficult to tell apart from Fusarium Ear Rot, the two can be distinguished easily when Gibberella produces it's characteristic red or dark pink (purple) colour mould. Infection begins through the silk channel and thus, infection in most cases starts at the ear tip. In severe cases most of the ear may be covered with mould growth.

Gibberella Ear Rot is economically important not only because of the potential yield and quality losses but because Gibberella zeae and Fusarium graminearum produce two very important mycotoxins that occur in Ontario, deoxynivalenol (vomitoxin or DON) and zearalenone.

These mycotoxins are especially important to swine and other livestock producers since they can have a detrimental affect on their animals. Feed containing low levels of vomitoxin (1ppm) can result in poor weight gain and feed refusal in swine. Zealalenone is an estrogen and cause reproductive problems such as infertility and abortion in livestock, especially swine. Feed grain that originated in a field with 5% or more Gibberella ear rot should be tested for these toxins.

Unlike Gibberella, Fusarium infected kernels will be scattered around the cob amongst healthy looking kernels or on kernels that have been damaged for example by corn borer or bird feeding. Fusarium infection produces a white to pink or salmon-coloured mould. A "white streaking" or "star-bursting" can be seen on the infected kernel surface.

Although many Fusarium species may be responsible for these symptoms, the primary species we are concerned about in Ontario is Fusarium verticillioides (formerly Fusarium moniliforme). The significance of this fungus is that it produces a toxin called fumonisin that has been shown to cause cancer (carcinogen) in humans. Fumonisin does occur in Ontario but rarely in any significant levels especially when compared to the Midwestern US.

When ear rot is present, the following storage and feeding precautions are advisable:

• Harvest as early as possible.
• If bird damage is evident, harvest outside damaged rows separately. Keep and handle the grain from these rows separately.
• Adjust harvest equipment to minimize damage to corn. Clean corn thoroughly to remove pieces of cob, small kernels and red dog.
• Cool the grain after drying.
• Clean bins before storing new grain.
• Check stored grain often for temperature, wet spots, insects and mould growth.
• Control storage insects.
• Exercise caution in feeding mouldy corn to livestock, especially to hogs. Pink or reddish moulds are particularly harmful. Suspect samples should be tested for toxins.

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