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.

* What about storing infected grain?

Drying won't reduce scab or DON levels, but drying prevents further fungus development. The moisture content of scabby grain going into storage should be about 12 percent. Scabby grain should not be comingled with good grain in storage.

For more information, go to www.ndsu.nodak.edu/plantpath/scabbygrain.htm for the publication "Dealing With Scabby Grain, Vomitoxin."