Posted 19 July 2010. PMN Crop News.
Fusarium Head Blight Leads to DON Contamination in Wheat
Source: Purdue University Press Release. www.ag.purdue.edu
West Lafayette, Indiana (July 14, 2010) - Indiana's wheat harvest is well under way, but with high levels of Fusarium head blight in many fields some of the crop is contaminated with the mycotoxin deoxynivalenol, or DON.
DON is produced by the fungal pathogen that causes Fusarium head blight, also known as head scab. It can harm many livestock, but is especially toxic to swine, said Charles Woloshuk, Purdue Extension plant pathologist.
"If wheat fields have not been harvested yet, farmers should check fields to determine if scabby grain is present," he said. "If the disease is present, increasing the fan speed on the combine can blow out the lighter scab-infected kernels, which contain most of the DON."
Livestock fed DON-infected grain can refuse feed, leading to poor weight gain. Hogs are most sensitive to the mycotoxin--even at one part per million (ppm) contamination. Cattle, sheep and poultry are more tolerant, however, and diluting scabby wheat with normal quality grain may be a way to safely feed wheat to livestock.
The concentrations recommended for livestock consumption are as follows:
• Swine: 5 ppm, but not to exceed 20 percent of the ration with finished feed at 1 ppm.
• Ruminating beef and feedlot cattle more than 4 months old: 10 ppm, not to exceed 50 percent of the diet with finished feed at 5 ppm.
• Poultry: 10 ppm, not to exceed 50 percent of the diet with finished feed at 5 ppm.
Farmers who want to determine whether their grain has DON should have the crop tested. Testing facilities in Indiana that analyze grain for DON are available in the Purdue Extension bulletin "Diseases of wheat: Fusarium head blight" found at www.extension.purdue.edu/extmedia/BP/BP-33-W.pdf.
If DON contamination is found in grain, farmers need to be aware that drying and storage will not reduce the levels. If handled properly, DON levels will not increase once grain is harvested and stored.
"The fungus requires 22-25 percent moisture content to grow," Woloshuk said. "At moisture levels below 18 percent, the scab fungus won't continue to grow. Moisture content of scabby grain going into storage should be below 13 percent."
When storing scabby grain, Woloshuk also recommends against mixing it with good quality wheat. That is because the light, thin kernels caused by head scab tend to accumulate in the center of the storage bin and can result in hot spots fine material with higher moisture content present in the core as well.
Using a cleaner to remove fine material from the wheat before binning and a grain spreader to distribute scabby kernels more evenly will minimize spoilage risks. If a cleaner and spreader aren't available, wheat should be cored as soon after binning as possible.