MOUNT PLEASANT, Mich. (AP) -- A salmon-colored fungus
[Fusarium graminearum, which produces deoxynivalenol] a vomit-
inducing toxin [vomitoxin] ...is making it more difficult for farmers to
get top dollar for their wheat. Fusarium head blight, also known as
wheat scab or tombstone, ... [is] infecting wheat fields throughout
Michigan and could affect 95 percent of farmers in Clare, Isabella, and
Gratiot counties.

"Very few fields are completely clean," said Paul Gross, Michigan State
University Extension director for Isabella County. ... [Scab cuts yields
by 30 to 40 percent, quality is reduced] and ... [high levels of
vomitoxin cut prices].

Scab, which can appear as bleached heads or [as] ... pink to orange
spots, infects wheat during the flowering stage and kills the top of the
wheat head. The resulting dead kernels are worthless. Vomitoxin,
while not fatal, can cause severe vomiting at high doses. Levels of
vomitoxin must be less than 0.4 parts per million for a premium and
less than about 1.5 parts per million to qualify as flour-quality.
Clinton and Shiawassee counties are registering 2 and 3 parts per
million,"Gross said.

Some spray fungicides are available to treat the problems, but permits
were obtained too late for best effect and the economics are deterring
some farmers, Gross said. Michigan State University conducted a
random test of 10 samples Thursday that revealed vomitoxin results
ranging from 0.3 to 2.2 parts per million.

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

[The International Maize and Wheat Improvement Center (CIMMYT)
based in Mexico regards Fusarium head blight (FHB) as a major factor
limiting wheat production in many parts of the world. Results of recent
research lead to the speculation that _Fusarium graminearum_ consists
of 7 genetic lineages which may eventually be regarded as species.
These phylogeographical lineages appear to have originated in different
regions of the world: Southern Hemisphere (2 in South/Central
America, 3 in Africa) and the Northern Hemisphere (2, one of which is
restricted to China). At least 4 of these can cause typical Fusarium head
blight disease in wheat.

The chemical name for vomitoxin is
12,13.Epoxy-3,7,15-trihydroxytrichothec-9-en-8-one deoxynivalenol;
dehydronivalenone. The US FDA lists the following vomitoxin levels
as safe for consumption by:

- Humans: One part per million (ppm) for end grain products;
- Cattle over 4-months old: 10 ppm, when grain with that amount of
vomitoxin does not exceed 50 percent of diet;
- Poultry: 10 ppm, when grain with that level of vomitoxin does not
exceed 50 percent of diet;
- Swine: 5 ppm, not to exceed 20 percent of ration;
- Other animals: 5 ppm if grains don't exceed 40 percent of diet.

Useful references include the following:
<http://www.apsnet.org/education/feature/FHB/Top.htm>
(good general article on FHB)

<http://www.cdl.umn.edu/scab/how_many.html>
(speciation in _F. graminearum_)

An excellent paper describing phylogeographic aspects of _F.
graminearum_: O'Donnell, K., et al., 2000. Gene genealogies reveal
global phylogeographic structure and reproductive isolation among
lineages of _Fusarium graminearum_, the fungus causing wheat scab.
Proc. Natl. Acad. Sci. USA 97:7905-7910. - Mod.DH]