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July
28, 2005
[ This story goes
with the Grain Containing DON Safe as Cattle,
Sheep Feed story. ]
NDSU Offers
Harvesting Tips for Dealing with Scab-infected Grain
Fusarium head blight,
commonly known as scab, has noticeably increased in occurrence and severity
in wheat and durum fields over the past week, according to Marcia McMullen,
North Dakota State University Extension Service plant pathologist.
“Severe levels
were observed in some winter wheat and spring wheat fields last week in
counties in the southeast, east-central and central parts of the state,”
McMullen says. “Now symptoms of the disease also are starting to
show in fields in more northern counties.”
A fungus, Fusarium
graminearum, which may invade developing small-grain heads from flowering
through kernel development, causes scab. Scab infection is favored by
long periods of high humidity and high dew points that coincide with flowering
and grain fill. Those conditions were common in some areas of North Dakota
this year because of record rainfalls in June.
Growers with severe
scab in their fields may take several steps to reduce their risk of harvesting
grain with high levels of scabby kernels and DON (deoxynivalenol or vomitoxin).
The following questions have been asked and the answers are based on experience
with scab epidemics:
Q: Will I have any
insurance or disaster payments?
A: Before harvest,
contact your insurance agent and the local Farm Service Agency to determine
if any crop loss will be covered and to learn what insurance contracts
require for loss coverage.
Q: Should I swath
or straight cut fields with scab?
A: Consider straight
combining to minimize further development of the disease or DON production
in the swath. Although swathing generally is used to bring down grain
moisture levels faster than with straight cutting, swathing onto wet
ground or getting rain on the swath could cause molding and further
grain deterioration.
Q: Are there ways
to minimize scabby kernels and DON in the harvested grain?
A: Severely infected
fields or portions of fields should be harvested and stored separately,
if possible or practical. Scab severities and DON levels likely will
be higher in portions of a field adjacent to drown-outs or in very low
areas. Also, research at Michigan State University showed that the highest
concentrations of DON were along field margins and in headlands in fields
that had no problems with drown-outs.
Use mechanical separation
of scabby grain. Set the combine fan speed to blow out shriveled, diseased
kernels that cause marketing and storage problems. Scabby kernels in
the harvested grain may add to yield, but will diminish market price.
Additionally, harvested
grain can be further cleaned by gravity tables, which may reduce the
level of scab enough to achieve top market grade and price in the cleaned
sample.
Farm workers and
grain handlers should minimize exposure to grain dust in fields with
scab. They should use enclosed cabs with good air filtration systems
and use dust masks when transferring grain.
Q: What can be done
with scabby grain that can’t be marketed?
A: NDSU studies
show that cattle and sheep mostly are DON tolerant. Hogs are sensitive
to DON, even at one part per million (ppm) hog feed contamination. The
toxin also can cause problems in horses, dogs and other single-stomach
animals. With any questionable grain, contact an Extension Service livestock
specialist, veterinarian or feed specialist before feeding DON-infected
grain to livestock.
The Food and Drug
Administration has guidelines for DON levels in grain:
- 1 ppm for finished
grain products for human consumption (many food processors and malt
barley companies have stricter requirements)
- Cattle more than
4 months old: 10 ppm (providing the grain at that level doesn’t
exceed 50 percent of the diet)
- Swine: 5 ppm (providing
grain at that level doesn’t exceed 20 percent of diet)
- Poultry: 10 ppm
(providing grain at that level doesn’t exceed 50 percent of diet)
- All other animals:
5 ppm (providing grain at that level doesn’t exceed 40 percent
of diet)
Straw from scab-infected
fields should be suitable for cattle and sheep bedding, but is not recommended
for horses.
For more information,
go to www.ndsu.nodak.edu/plantpath/scabbygrain.htm
for the publication “Dealing With Scabby Grain, Vomitoxin.”
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Source:
Marcia McMullen, (701) 231-7627, mmcmulle@ndsuext.nodak.edu
Editor: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.edu
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