August 9, 2005
From: ProMED-mail <promed@promedmail.org>
Source: GrandForksHerald.com, 9 Aug 2005 [edited] <http://www.grandforks.com/mld/grandforks/business/12336166.htm>

Scab scars wheat crop

When it comes to the Northern Plains spring wheat crop, looks may be deceiving. "There are pretty good stands from the road," says Jim Peterson, North Dakota Wheat Commission marketing director. However, a walking tour of fields reveals that leaf diseases and Fusarium head blight have taken more of a toll on some stands than appears during a "windshield" tour, Peterson says. Peterson said that once we got into the fields, the crop was "not as good as anticipated."

Crop scouts who participated in the annual tour of spring wheat and durum fields in northern South Dakota, North Dakota and western Minnesota spent 3 days in late July [2005] walking over hundreds of wheat fields to analyze
yields and quality.

Scouts, farmers and other crops experts say damage to the wheat from Fusarium head blight, commonly known as scab, appears to be primarily in northeast North Dakota and northwest Minnesota fields [which share a common border. - Mod.JW]. While the crop was planted early and had potential to be excellent, excessive rains, heat and high humidity trimmed yields, Peterson says. "We just didn't get some of those breaks along the way to help keep it at the top."

In Grand Forks County, where record June rains fell in some areas, scab is the most severe it has been in 5 or 6 years, says Ken Nichols, Grand Forks County extension agent. The disease is worrying farmers, because they know it will result in fewer bushels in the hopper, Nichols says.

Because the excessive rains and heat were prevalent in June, scab appears to have had a greater effect on wheat yields than on wheat quality, says Marcia McMullen, North Dakota State University Extension Service plant pathologist in Fargo. When the disease hits early in the flowering period, it prevents the wheat heads from completely filling or produces shriveled kernels, thus less wheat is delivered to the combine hopper. That's in contrast to the quality damage that results when scab hits later in the flowering period, McMullen explains.

In northwest Minnesota, early wheat harvest reports indicated that wheat quality is pretty good despite the most severe scab infestation the area has had in 10 years, says David Torgerson, Minnesota Association of Wheat Growers spokesman. Farmers hope that will remain the case when harvest gets into full swing during the next week. "They're hopeful they'll be able to blow out scabby kernels and end up with decent quality in the trucks."

However, northwest farmers are anticipating lower average yields than the record breaking 58 bushels per acre they produced in 2003 or the 55 bushel-per- acre crop they harvested in 2004, Torgerson says.

"We were set up in April and May (so) we could have had those high yields again. Conditions were right, then we started getting rains." The rains knocked down the yield potential one notch and scab lowered it another, Torgerson says.

In western North Dakota, hot temperatures appear to have reduced yields in the early wheat crop, Peterson says. Although double or triple the amount of rain fell in the west this year than fell last year, harvest test weights are
lighter, and yields are lower that farmers anticipated, Peterson says. Last year, aided by cool temperatures, farmers' wheat fields produced yields of 25 to 30 bushels per acre.

[Byline: Ann Bailey]

--
ProMED-mail
<promed@promedmail.org>

[Wheat scab has plagued some farmers in the northern plains states of the United States and some provinces in Canada. Farmers are concerned about the lower quality of the wheat crop, especially after experiencing 2 successive years of high yields. They will have to do a good job of seed cleaning to aximize their yield. Wheat scab (a.k.a. scab or head blight) is caused by fungi in the genus _Fusarium_, mainly _F. graminearum_, _F. avenaceum_, _F. culmorum_, and _F. nivale_. These Fusarium species are all asexual forms that produce only conidia. The sexual stage is _Gibberella zeae_.

Scab-infected wheat seed that is planted may develop root rot as well. These Fusarium fungi are ubiquitous and unfortunately can also cause a seedling blight and stalk, ear, and root rot of corn. A major concern is the presence of several important mycotoxins that can be produced in grain affected by scab. These toxins are produced by growth of the Fusarium fungi in the kernels, and ingestion of them can cause vomiting, nausea, dizziness, diarrhea, and muscle spasms in non-ruminant animals. Highly sensitive laboratory tests are currently used to detect mycotoxin contamination in grain. Thus, the chances of toxic compounds getting into human food is almost nil. The problem arises when farm livestock are fed uncleaned scabby wheat, oats or barley. 3 percent or more scabby kernels in feed may be poisonous to hogs. Hogs fed 10 percent or more scabby grain may vomit and refuse to eat the grain mixture. Cattle, sheep and mature poultry are much less susceptible to the mycotoxins. These toxins are quite stable and may remain in grain stored indefinitely.

Disease management involves crop rotation with legumes or other non-cereal crops; planting only seed that has been thoroughly cleaned and treated with recommended fungicides; using deep plowing to completely cover crop residues so as to reduce head-blight infections; and planting less-susceptible wheat cultivars where possible.

Links:
<http://www.ag.uiuc.edu/cespubs/pest/articles/200309f.htm>
<http://www.apsnet.org/education/feature/FHB/>  
- Mod.DH]

[see also in the archive:
Wheat diseases, cereals - USA (ND) 20050731.2227
Wheat diseases - India 20050615.1683
2002
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Fusarium head blight, oats - Canada (Manitoba) 20021017.5573 2001
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Fusarium head blight, wheat - USA (Michigan) 20010725.1452
2000
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Fusarium head blight: biological control 20000824.1416
Fusarium head blight, cereal - Canada (Manitoba) 20000823.1405 Fusarium head blight fungicide approved - Canada 20000624.1038 1999
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Scab disease, wheat - Canada, USA 19990508.0756
Scab-resistant wheat, McVey cultivar - USA 19990801.1311]