Tips on Storing Scabby Wheat

South Dakota State University Extension Plant Pathologist Marty Draper says that if scab-infected wheat is above 20% when put into storage, the fungus associated with scab could spread. There won’t be additional damage to kernels from scab at that point, but there could be more DON produced by the mold on scab-infected grain.

No more kernels will have symptoms of scab than when they went in to storage, but the resumption of growth by the fungus could infect grain kernels adjacent in the pile and resume production of mycotoxins.

There is no known evidence of scab or vomitoxin increasing in storage if grain is stored at appropriate moisture levels. Evidence also has shown that survival of the Fusarium fungus decreases with time in storage under proper storage moisture. The fungus requires 22 to 25% moisture content to grow. At that moisture level in storage, it is likely that other bacteria and fungi will out-compete the Fusarium fungus.

In one research study the fungus species that causes scab infection and produces DON remained viable during storage at 18 and 20% moisture, but that fungus species died during storage at 16% moisture. This means that DON production during storage is unlikely for wheat stored at less than 16% moisture.

SDSU Extension Farm Machinery and Safety Specialist Dick Nicolai says moisture content of scabby grain going into storage should be about 12%. Test grain for vomitoxin at a moisture content of 14 to 15% or lower for accurate readings.

Damaged grain is more susceptible to storage problems, Nicolai added. The light, thin kernels caused by scab tend to accumulate in the center of a storage bin, and hot spots may occur if higher moisture, fine material is present in the core as well. Using a cleaner to remove fines from the wheat before binning and a grain spreader to distribute scabby kernels more evenly will minimize spoilage risks, Nicolai says, and if a cleaner and a spreader are not available, he advises the wheat be cored as soon after binning as possible.

Drying won’t reduce scab or vomitoxin levels, Nicolai said, but does prevent further fungus development. Drying does not increase vomitoxin levels either.

North Dakota State University Extension Ag Engineer Vern Hofman says that the best cleaning may require a fanning mill (for air cleaning) and a gravity table, which will separate grain by test weight. However, in heavy scab infestations, a gravity table may not provide significant improvement in grain quality if many moderately infected kernels are present. Infected kernels are approximately the same size and density as uninfected kernels.

Cleaning infected grain with a fanning mill will reduce scab and vomitoxin levels, but air cleaning will result in a significant loss of nonscabby grain as well because of the air levels needed to get rid of the scabby grain, he says.

To determine if cleaning is going to be profitable, producers should compare the price for scabby grain to the cleaned-grain price, minus the cleaning cost. Cleaning may pay for some producers and not for others, Hofman notes. The scabby portion may be sold for ruminant livestock feed so long as it does not contain prohibitive levels of vomitoxin. 

The threshold for cattle more than 4 months old is 10 ppm, providing the grain at that level doesn’t exceed 50% of the diet.  Food and Drug Administration guidelines for DON levels in grain are no more than 1 ppm for finished grain products for human consumption (many food processors and malt barley companies have stricter requirements).

When storing scabby grain, try not to co-mingle it with grain from previous years. If possible, store this year’s grain from scabby fields separately from grain that has no signs of scab.

SDSU Extension Marketing Specialist Al May advises producers to visit with their local crop insurance agent if they anticipate filing a crop insurance claim for losses due to scab.