Scant FHB, DON in Northern Plains Wheat, Barley

While FHB or scab was a problem east of the Mississippi River this year, drier weather conditions in the Northern Plains set up wheat and barley crops which generally yielded well with good quality. 

Levels of FHB in the Canadian prairies this year were lower than they have been for over 20 years, with growers in western Canada harvesting a high quality crop in 2003, according to Randall Clear, mycologist with the Canadian Grain Commission’s Grain Research Laboratory.

Across the border in North Dakota, the level of FHB in wheat was the lowest observed since 1992, according to Marcia McMullen, NDSU extension plant pathologist. The disease was observed in 35% (129 out of the 370) of wheat fields that were surveyed in the state past the flowering stage.  However, the average field severity was only 2.3% in those symptomatic fields.  The majority of fields with symptoms were in the
northeast part of the state. Overall, wheat fields surveyed past the flowering stage (including those without symptoms), the average field severity was only 0.8%, according to McMullen.

Shaukat Ali of NDSU coordinated a small grains disease forecasting system to help track small grains disease development in eastern N.D. and western Minn., online at www.ag.ndsu.nodak.edu/cropdisease .

Marty Draper, South Dakota State University plant pathologist, says that early in the growing season, leaf diseases (rusts, tan spot, septoria blotch) appeared to be prevalent across southeastern S.D., and high levels of precipitation with periods of warm weather also encouraged the growth and development of the scab pathogen, Fusarium graminearum.  Drier conditions later in the growing season improved the chances for a quick harvest, and high quality grain, Draper says. Draper coordinated a wheat scab risk advisory web site this year (http://plantsci.sdstate. edu/wheatpath/riskadvisory. html) covering a number of northeastern S.D. counties.

Only 22 of 215 crops sampled in 2003 showed symptoms of FHB, as part of the annual IPM barley crop pest and disease survey. The mean scab index of the infected crops was 1.6 and the mean over all crops was 0.16.  This is a very low mean scab index over all crops.

Incidence of infected heads, average percentage of head infected and scab index (incidence x percentage of head infected) was determined in all crops sampled past the kernel watery ripe stage. The survey is conducted by the Barley Pathology laboratory in the Department of Plant Pathology at NDSU. The SBARE Malting Barley for Western North Dakota project and the American Malting Barley Association provide financial support for the survey, and sample collection is conducted by crop scouts at Dickinson Research and Extension Center, North Central Research and Extension Center and at Fargo.

The regions in which infected crops were found varied over the season and possibly reflect climatic conditions during ripening in those regions. One early and severely infected crop was found in southwest N.D. As the season progressed, no more infected fields were found in the southwest, but infected fields were found in the northeast and east central regions of N.D. In the latest maturing crops, infected fields were found in the northeast and north central regions of the state.

DON (deoxynivalenol, or vomitoxin) levels were determined in 317 samples from the 2003 crop in North Dakota, Minnesota and South Dakota, as part of the annual barley crop survey. The survey is conducted by the barley quality laboratory in the Department of Plant Sciences at NDSU. The North Dakota Barley Council and the AMBA provide financial support for the survey, and sample collection is conducted by the ND Agricultural Statistics Service. The USWBSI provides financial support for the analysis of DON.

The average DON level of the 2003 crop was 0.4 ppm (mg/kg) and approximately 73 % of all samples were below 0.5 ppm.  This is the lowest regional DON level that has been observed since DON analysis was incorporated into the survey in 1993. DON levels averaged over 2.0 ppm in 2001, 2000, and 1993-1998. As little as 16% of the barley crop was DON free (<0.5 ppm) in some of these years. 

The 2003 crop represents a slight improvement over 2002 when the regional barley crop averaged 0.7 mg/kg DON, with 69% of the crop below 0.5 ppm. However, in 2002 approximately 30% of the regional crop exhibited pre-harvest sprouting, and overall grain quality was poor. In 2003 the low DON occurrence, coupled with excellent crop quality, has been a boon to regional growers and the malting, brewing and feed industries.

The highest single occurrence of DON in 2003 was 5.6 ppm, which compares to maximum levels in excess of 20 ppm in previous years. Little to no DON was observed in barley samples collected from the 3 western districts of North Dakota, south central N.D. and northeastern S.D.  DON was found, albeit at low levels, in eastern N.D., central to north central N.D., and the two western districts of Minnesota. These are the regions where occurrence of FHB has historically been the highest. Overall, the greatest incidence of DON was seen in east central N.D. and western Minnesota, where 50-80% of samples collected tested at >0.5 ppm.

—Stephen Neate, plant pathologist; Paul Schwarz, plant scientist, North Dakota State University

Fungicide Continues to Perform Well
In NDSU fungicide field trials this year, under mist and artificial inoculation, there was a 72% reduction in FHB with Folicur (applied at the labeled rate of 4 fl oz/ac), though FHB levels were low compared to previous years, with only a 10.2% field severity, according to NDSU extension plant pathologist Marcia McMullen.  In the absence of severe FHB, Folicur did a good job on leaf diseases, which were severe in test plots and in many commercial fields, she notes.

Blaine Schatz at the NDSU Carrington Research Extension Center, saw a 13.5 bu/acre increase over the untreated check with a Folicur treatment on spring wheat and a 10.8 bu/acre increase with Folicur treatment on durum.  Commercial spring wheat producers in the Valley City area documented 13.6 bu/acre yield increase with Folicur treatment, (their treated fields averaged 88.5 bu/acre) although their untreated check still yielded a whopping 74.9 bu/ac. Thus, in eastern N.D., many growers had excellent yields this year,  but some did even better with a fungicide treatment.

FHB Plagues Wheat in Eastern U.S.
While the Northern Plains was enjoying its best wheat and barley crops in years, scab and DON plagued wheat crops east of the Mississippi. 

Large amounts of rainfall was the main culprit behind North Carolina’s worst wheat production in 17 years.  About half of the wheat produced in North Carolina this year is unsuitable for human consumption, according to Paul Murphy, professor of crop science at North Carolina State University.

FHB not only wreaked havoc on wheat yields, Murphy says, but also resulted in various levels of DON or vomitoxin.  While DON in large doses can be detrimental to animal and human health, Murphy stresses that there is no danger to the food supply, since there are strict guidelines on the amount of allowable DON—essentially less than two parts per million for human consumption and five ppm for animal feed.  These guidelines set by the federal government are monitored by mills that process wheat into flour.

Still, FHB damage to farmers and millers in North Carolina this year was unprecedented. “Yields were off by about 20% and harvested wheat has terribly poor quality,” Murphy says. While wheat doesn’t command the attention or acreage of tobacco or corn in North Carolina, it is still big business for scores of farmers and millers. North Carolina produces the largest amount of wheat in the southeast U.S.; the crop is worth anywhere from $50 to $80 million each year. Most wheat grown in the state is soft red winter wheat, planted in October and harvested in June.

According to Mike Pate, Mid-States Mills in Newton, N.C., area mills are being forced this year to haul winter wheat from a variety of sources across the Southeast, costing mills more money in freight charges.

Pate says that Mid-States Mills operates on fixed contracts with cake, pastry, cookie and doughnut producers, who pay for a specific amount of flour. If the supply of quality wheat is insufficient, mills must find wheat from other regions to produce enough flour to hold up their end of the contract.

Murphy points out that one miller, who transferred operations to North Carolina from the Red River Valley region about five years ago, said that the impact on his operation was worse in North Carolina this year than in the spring wheat region epidemics of the early 1990s.  “I understand this to be a reflection of the better infrastructure with respect to the supply chain in the Northern Plains,” he says.

Murphy and Randy Weisz, NC State associate professor of crop science and small grains extension specialist, put together a management fact sheet for area wheat farmers to help ward off another wheat scab epidemic next year.  Better varieties will help; Murphy and researchers at Virginia Tech University have produced a number of moderately resistant varieties of soft red winter wheat. 

This and other FHB research, such as screening germplasm and varieties for FHB resistance, is funded in part by the U.S. Wheat and Barley Scab Initiative.  “Our ‘moderately’ resistant varieties are only a small step in the right direction,” Murphy says, pointing out that a multi-faceted approach is needed to bring FHB under control.

“The only positive footnote from this epidemic was the confirmation that several varieties (NC-Neuse, Roane, Tribute and McCormick), previously identified in USWBSI funded screening nurseries, exhibited moderate levels of FHB resistance in commercial production,” says Murphy.

In Indiana, FHB incidence in most fields ranged between 10 and 70%, according to Purdue agronomist Herb Ohm. Spread of the disease after infection was delayed due to unusually cool day and night temperatures, but about 3 weeks after flowering temperatures became higher (normal) and the disease did spread significantly, late in grain fill. “Certainly, Fusarium was the most significant disease (this year) in wheat in Indiana,” says Ohm.

Rainy, humid weather during grain flowering also caused FHB problems in Pennsylvania.  Scab incidence in Pennsylvania soft red winter wheat fields averaged about 30%, and many producers in the state struggled with DON, leaving them with grain that could not be marketed, according to Erick DeWolf, plant pathologist at Penn State. Scab also affected barley grown in the state.

Don Hershman, University of Kentucky extension plant pathologist, says that the FHB situation in 2003 was the worst since the area’s FHB disaster in 1991, though the problem this year was nowhere near as widespread and devastating as it was in 1991.

Overall, FHB symptom expression was highly variable, Hershman says. Crop flowering date, as related to variety and planting date, appeared to be a significant variable impacting FHB. There was a two-week window in May during which most of the wheat in Kentucky flowered. The first week was highly favorable to FHB infection; the second week, generally, was not. The fields hit most with FHB were the ones that flowered during the first week. Those that flowered during the second week had significantly less FHB.

Because of an unusually long grain fill period last spring, many farmers that had significant FHB in their crop still harvested grain with higher than average test weights, Hershman says. Much of this grain, however, had excessive DON accumulation which has seriously impacted the use of Kentucky wheat by millers and certain other end users.

2003 Cereal Rust Summary

The USDA-ARS Cereal Disease Lab in St. Paul issued the following summary of cereal rust in the U.S. in 2003:

•  Stem rust was found throughout the northern Great Plains on wheat, barley and oat, but developed too late to cause any yield loss.

•  Wheat leaf rust was widespread and severe in some areas of the U.S.

•  Wheat stripe rust developed early and was more severe than usual throughout the U.S.

•  Oat stem and crown rust severities were light this year.

•  Stem rust infection on barberry in Minnesota was the most severe in the last 40 years.

A complete report can be found online at www.cdl.umn. edu .