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Crop Advisor’s Solution – for Apr. 4, 2011

Tim’s cattle won’t be dining on corn any time soon. Last November, while fencing off a field of grazing corn, previously badly damaged by hail, this Saskatchewan producer noticed a distinctly musty smell coming from the crop.

Concerned his corn was rotting due to the damage caused by the hail, Tim called me right away before allowing any cattle into the field to graze.

I visited Tim’s 3,000-acre mixed cattle and grain operation the next day. The half section of grazing corn had been severely damaged — the stalks were bent over or broken off — and the field smelled musty. I checked the bases of some of the stems and I found mould growing, but the growth was minor.

I broke open one of the stalks and found an orange and pink fungal infestation lining the inside of the stem. Rather than jump to any conclusions, I sent the sample for analysis. The tests were conclusive — the results showed the sample contained the fungal species Alternaria, Aspergillus, Fusarium and Penicillium, all well over the acceptable levels for feed use.

Although high levels of mould can cause respiratory problems and lessen the palatability and nutritional quality of the plant material, it does not necessarily condemn the crop as unusable for feed. But in this case, the news couldn’t have been worse.

The moulds found in Tim’s field were the mycotoxin-producing species. For example, the toxin zearalenone, which is produced by F. graminearum, causes a number of adverse health effects in cattle, including a high rate of abortion. A mycotoxin panel confirmed this crop was unsuitable for cattle feed. The incidence of disease could have been decreased in this field by spraying a fungicide on the crop after the hailstorm damaged the corn to prevent fungi from entering the plants.

Unfortunately for Tim, there is no other use for a crop contaminated in this way, and producers caught in this situation are forced to dispose of as much of the plant material as possible. F. graminearum is saprophytic in nature, meaning it has the ability to feed off of dead plant material. Residue left in the field allows the fungus to further colonize the stalk and root mass, increasing the number of spores and potential of further infection.

Implementing a crop rotation that aims to decrease the conditions favourable to fungal infestations is important for producers in regions known to be prone to disease, or when environmental conditions — such as heavy precipitation and warm temperatures — are conducive to the spread of disease.

Although Tim had not seeded corn on that field in four years, the north quarter was seeded to durum and the south quarter to canola in 2009. That year, durum was under high disease pressure from Fusarium. In addition, 2010 was a very wet year, ideal for the spread of disease. Seeding corn on this field in such a tight rotation with a cereal guaranteed an increased incidence of disease. In future, Tim will work in pulses and oilseeds to break up the rotation of cereals and corn.

Some research has revealed the expansion of F. graminearum into areas that primarily grow small grain cereals has been accelerated by including corn in the rotation.

For the next few years, Tim will stay away from seeding cereals on this half section. Going forward, planting an oilseed on this field next year is a good bet for Tim, since an oilseed would be the least susceptible to any inoculum present in the soil.

AngelaMcKagueisanareamarketing Corinne,Sask.



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