CROP DISEASES
MAJOR DISASTERS
WHEAT & BARLEY BLIGHT
FUSARIUM HEAD BLIGHT (FHB)
SCENARIOS 808, 444, 277, 013, 02
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Vomitoxin levels rise in wheat samples across nine U.S. states
Fusarium head blight of wheat (FHB), also known as ‘head scab,’ is caused mainly by the fungus Gibberella zeae (aka Fusarium graminearum). The disease has previously caused significant yield loss and reduced grain quality in the U.S. costing the industry about $3 billion from 1998 to 2000, and more than $4.5 billion in 2011. Gibberella zeae also produces mycotoxins—chemicals that are toxic to humans and livestock.
The fungus has plagued the soft red winter (SRW) wheat, which develops when it rains during the crop’s key growing stages.
As little as two or three days of light to moderate rainfall can favor infection. Optimum temperatures for infection are between 75°F and 85°F, but during prolonged periods of high humidity and moisture, infection will occur at lower temperatures. The initial infection on the wheat head may produce additional spores that can infect other wheat heads. This secondary infection can be especially problematic in uneven wheat stands with late flowering tillers.
Infection will continue as long as weather conditions are favorable and wheat plants are at susceptible growth stages.
Bleached and shriveled tombstone kernels (left) compared to healthy wheat kernels. Seed infected with Fusarium graminearum can produce seedlings affected by seedling blight when planted. Infected seeds will have poor germination and the resulting seedlings may be slow to emerge. Infected seedlings will be reddish-brown to brown, will lack vigor, and will tiller poorly. Source: Purdue Extension [BP-33-W]
SRW is grown in a large eastern section of the United States, in the south from Louisiana and Arkansas across to the Carolinas and in the north from Missouri across the Midwest to Pennsylvania and Maryland, accounting for a fifth of the U.S. total wheat crop in the last five years, said a report.
A preliminary survey conducted by the U.S. Wheat Associates showed composite vomitoxin level from more than 500 samples across nine states were about twice the five-year average of 1.3 ppm, said the report.
“We’re seeing about 10 ppm and I don’t know that we have seen that before. The elevators are not sure what they’re going to do with that wheat,” said a grain merchant at a milling company based in Illinois.
The U.S. Food and Drug Administration (FDA) limits vomitoxin levels in finished products such as flour to 1 ppm.
“It is in a lot of the wheat, areas east of the Mississippi River would be the most suspect, all along the U.S. Gulf and through the Eastern Seaboard. There were even high levels coming out of Pennsylvania,” said a livestock nutritionist at a feed company based in Kentucky.
Risk of Mycotoxins
Gibberella zeae produces the mycotoxin, deoxynivalenol (DON), also known as vomitoxin.
DON is an extremely stable mycotoxin and drying and storing grain will
not reduce DON levels in harvested grain.
The fungus may also produce another mycotoxin, zearalenone, however this mycotoxin is not as common in wheat as DON. Zearalenone has estrogenic properties, which means it can cause infertility, abortion, or other breeding problems. As little as 1 to 5 ppm zearalenone ina feed ration may produce an estrogenic effect in swine.
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