Date: August 10 2006
From: ProMED-mail <promed@promedmail.org>
Source: USDA Cereal Rust Bulletin 2006: Number 10, 9 Aug 2006 [edited] <http://www.ars.usda.gov/Main/docs.htm?docid=9757>


Wheat stem rust

Wheat stem rust was at low levels on susceptible winter and spring wheat.

The 1st reports of wheat stem rust were in mid-April 2006 in soft red winter wheat plots at Crowley, in south central Louisiana, with severities of up to 40 percent. Stem rust was found in 28 of the 102 plots, which were located near rice paddies. The regular dew formation in these plots provided a suitable environment for stem rust infections.

On 18 Apr 2006, wheat stem rust was at low levels in plots at Baton Rouge, Louisiana. These plots of wheat matured 14 days earlier than normal because of minimal rainfall. By late May 2006, severe stem rust was observed on late- planted wheat nurseries at this same location.

In late April 2006, wheat stem rust was found in a field in Ellis County in north central Texas. This was the first report of wheat stem rust in Texas in 2006.

In mid-May 2006, low levels of wheat stem rust were found in southwestern Georgia plots at Plains.

From collections made from the above locations, race QFCS was identified as the predominant race. This is a common race that has been found in the U.S.
the past several years. This race is relatively avirulent -- the majority of the U.S. cultivars are resistant to QFCS. Race MCCD (variant of old race 56) was found from a collection in Texas.

In late May 2006, traces of stem rust were observed on late-maturing lines of wheat at Kinston, North Carolina. In mid-July 2006, the susceptible spring wheat cultivar Baart in southern and west central Minnesota and east central North Dakota plots had trace to 10 percent severities of wheat stem. Race QFCS was identified from these collections.

In late July 2006, 5 to 10 percent stem rust severities were reported in plots of Baart in east central South Dakota and trace levels in northwestern Minnesota. All of the currently grown spring wheat cultivars are resistant to the prevalent U.S. races.

In late July 2006, low levels of wheat stem rust were found in plots at Colfax
in Whitman County, Washington. In early August 2006, light to moderate
levels of stem rust were observed in spring wheat plots in Aberdeen, Idaho.
The rust appeared to come in late as most infection was on late tillers or late maturing lines.

Stem rust observation maps are now available on the CDL website (<http://www.ars.usda.gov/Main/docs.htm?docid=9757>).

Wheat Leaf Rust

Wheat leaf rust was widespread and at low to moderate levels throughout the U.S

Southern Plains - Texas. The 2006 fall and winter were the driest on record in the state of Texas. In late January 2006, low levels of leaf rust were reported in irrigated central Texas wheat plots. In early March, leaf rust was found in varietal plots at College Station, Texas. In a few of the susceptible cultivars, e.g. Jagger, leaf rust severities of 5 percent were observed on the flag leaves and in a few others, e.g. Cutter in an early planted test, 70 percent severities were observed on the lower leaves. In mid- March 2006, only traces of leaf rust were found in the irrigated nursery at Castroville, Texas. The wheat crop throughout south Texas was under severe drought stress. By the 2nd week of April 2006, the susceptible cultivars Jagelene and Jagger had 80 percent leaf rust severities in nurseries at Castroville and College Station, Texas. In the highly resistant cultivars Fannin and Endurance, no infections were found. Only low levels of rust were reported in g!
rower's fields in southern and central Texas because of the dry conditions.

- Oklahoma. In mid-January, leaf rust was found in southern Oklahoma, but conditions were not conducive for infection, spread, and development of leaf rust. By the 1st week in March, a few pustules of leaf rust were observed on lower leaves in the wheat varietal plot at Stillwater, Oklahoma.

In late March 2006, low levels of leaf rust were reported in grower's fields in Oklahoma. On 1 May 2006, traces of leaf rust were found in plots at Stillwater in northeastern Oklahoma. This year leaf rust development was less than normal in Oklahoma because of drought conditions throughout the state.

Central Plains - Kansas. In mid-March, no rust pustules were found on wheat that previously had infections in late fall in Kansas. In late April 2006, traces of leaf rust were found in south central Kansas where wheat was under extreme drought stress. In mid-May 2006, low levels of leaf rust were found in fields and plots in central Kansas. During the 3rd week in May 2006, 1 percent severities were observed on flag leaves of susceptible cultivars in northeastern Kansas plots. This year leaf rust losses were less than normal in Kansas because of the persistent drought throughout much of the state.

- Nebraska. In early March, traces of leaf rust were found on the lower leaves of wheat in plots and fields in central Nebraska. In mid-May 2006, low levels of leaf rust were found on lower leaves of wheat plants in research plots in central Nebraska. By early June 2006, leaf rust developed to 15 to 25 percent severity levels on flag leaves in central and eastern Nebraska, and in irrigated wheat in southwestern Nebraska. As in the southern Great Plains, continued hot dry weather slowed leaf rust development in the central Great Plains.

Northern Plains - Minnesota, South Dakota, North Dakota. On 8 May 2006, leaf rust infections that had apparently over-wintered were found on the lower leaves of the susceptible winter wheat Cheyenne at the Rosemount Experiment Station in east central Minnesota. On 26 May 2006, 5 percent severities were found on flag-2 leaves in susceptible winter wheat plots at Rosemount. In early June 2006, traces of leaf rust were found on the spring wheat Alsen in Bottineau County in north central North Dakota, which is near the Canadian border. Drier than normal conditions in May 2006 and June 2006 slowed leaf rust development in most areas of the northern plains.

In late June 2006, plots of susceptible winter wheat cultivars in east central Minnesota and east central South Dakota had 60 percent rust severities, while resistant cultivars had only trace levels of infection on the flag leaves. By late June 2006, spring wheat had leaf rust severities of trace to 1 percent on lower leaves in southern Minnesota and North Dakota fields (for Fig. 1, see URL above). Susceptible spring wheat cultivars in southern Minnesota plots had 20 percent rust severities on the lower leaves.

In early July 2006, high levels of leaf rust were found in susceptible winter wheat in plots in southeastern North Dakota and in mid-July 2006 high levels of infection were found in spring wheat fields in north central North Dakota.

By mid-July 2006, trace to 60 percent leaf rust severities were observed on flag leaves of spring wheat cultivars in fields and plots from north central South Dakota to west central Minnesota. In late July 2006, wheat leaf rust was at trace to moderate severity levels in spring wheat fields in northern Minnesota and North Dakota. Plots of susceptible cultivars in the same area had moderate to high leaf rust severities.

This year leaf rust was widespread, but at lower levels than normal in the upper Midwest on both spring and winter wheat. Lower amounts of rust inoculum than in previous years arrived from the winter wheat region because of the persistent drought-like conditions in the southern plains, which reduced rust infections in the winter wheat. Hot and dry conditions in the northern plains in June 2006 and July 2006 also reduced the incidence and severity of leaf rust. Many spring wheat fields were sprayed with fungicide, further reducing leaf rust infections and also the incidence of leaf spot diseases.

Southeast - Louisiana. In mid-February 2006, leaf rust was found on susceptible winter wheat cultivars throughout Louisiana in plots and fields.
By early March, cultivars growing in plots in southeast Louisiana had up to 70 percent leaf rust severity. In late March 2006 in wheat plots at Alexandria, Louisiana, susceptible winter wheat cultivars had 20 percent leaf rust severities on the lower leaves. Some of the fields infected with rust were sprayed for rust control in the southern U.S.

During the 2nd week in April 2006, plots in southern Louisiana had leaf rust severities up to 70 percent. By late April 2006, plots of susceptible wheat cultivars in northeastern Louisiana had leaf rust severities up to 80 percent on flag leaves.

- Arkansas. In early February 2006, leaf rust had survived as far north as northeast Arkansas, however, a mid-February 2006 cold snap combined with freezing rain and snow appeared to kill the rust. In mid-March 2006, leaf rust was light in the southern part of the state. By mid-April 2006, leaf rust was found in areas of Arkansas that had sufficient moisture.

In late April 2006, plots in east central Arkansas had 0-50 percent leaf rust severities. In Arkansas leaf rust was more widespread than in the last few years, but the high severities occurred too late to cause much yield loss.

-Mississippi, Georgia, Alabama, South Carolina. In mid-March 2006, leaf rust was at low levels in southern Georgia plots. In early April 2006, leaf rust was found on the lower leaves of the most susceptible cultivars in southwestern and south central Georgia. In late April 2006, in the area from central Mississippi to central Georgia, plots of susceptible wheat cultivars had leaf rust severities up to 80 percent. Fields in the same area had
severities from 0 to 10 percent. In mid-May 2006, susceptible soft red winter wheat cultivars in northern Alabama plots had 60 percent severities. In early May 2006 flag leaves of soft red winter wheat in central South Carolina plots had 5 percent leaf rust severity. This year in the southeast U.S. leaf rust was widespread, but light and losses were minimal.

Mid-Atlantic - North Carolina. In late March, the cultivar McCormick in southeastern North Carolina plots had low levels of leaf rust on lower leaves. In the 2nd week in May 2006, severe leaf rust infections were reported in plots at the Kinston station in east central North Carolina. In North Carolina, wheat leaf rust was widespread in the central Coastal Plain and particularly severe in the Neuse River basin; only traces of wheat leaf rust were observed in the Piedmont.

- Virginia. In the 1st week in May 2006, severe leaf rust infections were reported in the wheat-breeding nursery at Warsaw in northeast Virginia. By mid-May 2006, wheat leaf rust was widespread and severities up to 65 percent were reported on susceptible cultivars McCormick (Lr24) and USG3209 (Lr26), in plots on the eastern shore of Virginia. Leaf rust was earlier and more severe than normal across the state of Virginia. There appeared to be little virulence to the Lr9 gene in the rust population, as Tribute, Coker 9835 and Coker 9663 were virtually clean. In contrast, there seems to be significant virulence to genes Lr24 and Lr26 and to a lesser extent, Lr18.

This year wheat leaf rust development was greater than normal in the Mid- Atlantic States and losses occurred in a few areas.

Pennsylvania. In early June 2006, leaf rust that over-wintered was limited to the lower canopy of wheat in Pennsylvania.

New York. In early July 2006, low levels of leaf rust were found in winter wheat plots at Ithaca, New York.

Midwest - In early June 2006, wheat leaf rust was found in fields from east central Missouri to southern Illinois at 20 percent severity on flag leaves.
The 1st report of leaf rust in Ohio was during the 2nd week in May 2006 in south central Ohio, where the rust May 2006 have over-wintered. By early June 2006, trace levels of leaf rust were found on flag leaves of wheat in fields from northwestern Ohio to south central Wisconsin. In mid-June 2006, plots in west central and northwestern Indiana had 40 percent severities on lower leaves.

By mid-June 2006, leaf rust was severe on the upper leaves of susceptible cultivars throughout the northern Ohio. More leaf rust was found in Ohio than last year, as moisture conditions throughout this area were conducive for rust development and some losses occurred in susceptible cultivars.

California - In mid-May 2006, leaf rust severities up to 80 percent were observed in susceptible cultivar plots in Kern County and Madera County late in the growing season.

Washington - In mid-July 2006, leaf rust was very light in experimental plots at Pullman and Mt. Vernon, Washington. No leaf rust was found in farm fields.

Idaho - In early August 2006, light to moderate levels of leaf rust were observed in spring wheat and triticale plots in Aberdeen, Idaho. The rust appeared to come in late as most infection was on late-maturing lines.

Preliminary race identifications - From rust collections made in early November in north eastern Oklahoma plots, the following leaf rust races were identified: TBBJ (Lr2a virulence), TDBJ (Lr24 virulence) and TDDS (Lr17 & 24 virulence). From collections made in early December [2005] in central Texas, the TDBJ (Lr24 virulence) race and in northwest Arkansas the TBRK (Lr11 and Lr18 virulence) race were identified. From collections made in early March [2006] in central Texas the following races were identified: TDBJ (Lr24 virulence), TJBG (Lr16 and Lr24 virulence) and MFPS (Lr17, Lr24, and Lr26 virulence). These leaf rust races also were identified from rust collections made during the 2005 leaf rust survey (<http://www.ars.usda.gov/mwa/cdl/>).

Wheat stripe rust

Wheat stripe rust was at low levels throughout the U.S. Southern Plains

- In early March, wheat stripe rust was present at low levels on the upper leaves of a cultivar growing in a plot at College Station, Texas. In mid- March 2006, traces of stripe rust were found in the nursery at Giddings in central Texas. In late March 2006, wheat fields and plots in southern and central Texas had low levels of wheat stripe rust. Conditions were not favorable for rust development (limited moisture and few cool nights). In early April 2006, only traces of stripe rust were found in southern and central Texas. By mid-April 2006, stripe rust had not been found in Oklahoma or states to the north. In late April 2006, hot and dry conditions slowed
stripe rust development in plots and fields throughout the southern U.S. This year stripe rust development in the southern plains was much less than last year because of the limited moisture and high daytime temperatures. The southern states provided a reduced amount of inoculum for the northern regions of the U.S. !

Central Plains - On 22 May 2006, traces of wheat stripe rust were found on the flag leaves of susceptible cultivars in plots at Manhattan, Kansas, but hot dry weather slowed further rust development. In early June 2006, traces of stripe rust were found in a winter wheat nursery at Mead in east central Nebraska and in winter wheat plots in northeast South Dakota. This year stripe rust was very light in the central and northern plains because inoculum from the southern plains was light and drought conditions persisted in much of the area.

Northern Plains - On 26 Apr 2006, light amounts of stripe rust were reported on winter wheat in plots at St. Paul, Minnesota. This may have been an over- wintering site. In early May 2006, stripe rust infections that had apparently over-wintered were observed on susceptible winter wheat cultivars in the Gallatin Valley in southwestern Montana. On 26 May 2006, flag leaves of susceptible winter wheat in east central Minnesota plots had 10 percent stripe
rust severities. By the 3rd week in June 2006, traces of stripe rust were
found on a few winter wheat cultivars in east central South Dakota and east central Minnesota plots. Hot weather slowed rust development in these plots.
Many wheat fields were sprayed with fungicide to prevent losses due to rust and scab. By mid-July 2006, hot dry weather had stopped most development of stripe rust on spring wheat in the northern Great Plains.

Cool and wet weather the first half of June 2006 were favorable to stripe rust development in Montana winter wheat. In central and east central Montana 15 000 - 20 000 acres of winter wheat were sprayed with fungicides. There were sporadic reports of stripe rust on spring wheat, but the severity was low.
Dry and warm weather in early July 2006 slowed stripe rust.

In mid-June 2006, wheat stripe rust foci of 60-80 percent severity where observed in winter wheat nursery plots at Winnipeg, Manitoba, Canada.
Infections were noted on lower leaves thus indicating that over wintering May 2006 have occurred. Very mild winter conditions with adequate snow cover occurred in 2005-2006, and near normal spring temperatures were favorable for stripe rust infection.

Louisiana - In mid-February, stripe rust was increasing in wheat plots at Winnsboro in north central Louisiana and by mid-March 2006 was severe throughout the plots. In mid-March 2006, stripe rust was severe on a few susceptible cultivars in the nursery at Baton Rouge, Louisiana. In late March 2006, some fields were sprayed for rust control. In wheat plots in south central Louisiana, susceptible cultivars had 60 percent stripe rust severities. Higher day and night temperatures during the last week of March slowed stripe rust development. In early April 2006, high levels of stripe rust were observed in northeast Louisiana plots, but infections in fields were light.

Arkansas - In early February, wheat stripe rust was found throughout Arkansas. However, a mid-February cold snap slowed rust development in the state. By mid-March 2006, only low levels of stripe rust in east central Arkansas had been found. In late March 2006, stripe rust was at low levels in fields in southern Arkansas. By early April 2006, stripe rust was increasing throughout Arkansas, but conditions did not favor development of high rust severities.

Southeast - In early April 2006, stripe rust was found in southern Georgia.
In late April 2006, high severities of stripe rust were observed in late maturing susceptible cultivars in the nursery at Plains in southwestern Georgia. In the nursery most of the stripe rust infections had occurred earlier in March and April 2006 when temperatures were cooler. By late April 2006 leaf rust was the most prevalent rust on wheat at Plains. In mid-May 2006, light levels of wheat stripe rust were found in Limestone county plots in north central Alabama.

Midwest - In early May 2006, plots in Urbana, Illinois had low levels of stripe rust incidence and severity. The drier and warmer than normal weather in April 2006 and May 2006 slowed the increase and spread of stripe rust. In early June 2006, traces of stripe rust were found in east central Missouri fields. In early June 2006, 40 percent wheat stripe rust severities were observed on flag leaves in plots in northwestern Indiana; trace severities were found in fields. The only report of stripe rust this year in Ohio was in a wheat breeding line. Last year stripe rust was found at a number of locations in Ohio.

North Carolina
- Heavy stripe rust was reported in fields in the Albermarle/Pamlico Sounds region in east central North Carolina in early May 2006. This year insignificant levels of wheat stripe rust were present throughout the Coastal Plain of North Carolina.

Virginia and Maryland - In mid-May 2006, hotspots of stripe rust were found in wheat plots in the eastern shore of Virginia and Maryland.

California - In mid-March, low levels of stripe rust were found in plots in the southern San Joaquin Valley. In March, California had cool and very wet conditions, which was favorable for stripe rust development. In early April 2006, the susceptible forage wheat cultivar Dirkwin had stripe rust severity of 30 percent in the Imperial Valley. Infections also were noted in fields of Orita durum wheat in the Imperial Valley.

Light infections of wheat stripe rust were reported in the southern portion of the San Joaquin Valley and more severe infections were reported from scattered areas further north in the San Joaquin Valley and throughout the Sacramento Valley. In some Sacramento Valley fields, 80 percent severities were recorded in hot spots. By late May 2006, wheat stripe rust was severe throughout the Central Valley of California. The 2 most widely grown cultivars, Summit and Blanca Grande, are now both fully susceptible to the races of stripe rust that occur in California. Statewide, yield losses to wheat stripe rust may approach 15 percent this season.

Pacific Northwest - By the 2nd week in April 2006, nursery plots at Mt. Vernon (northwestern Washington) had 40 percent stripe rust severity. Rust also was found in some surrounding fields. During the 2nd week in April 2006 wheat stripe rust was not found from central to eastern Washington. By the 3rd week in April 2006, susceptible entries in winter wheat nurseries at Mount Vernon in northwestern Washington had 60 percent levels of stripe rust infection. In south central and southeastern Washington, early-planted winter wheat fields had 5 percent stripe rust severity. In this area the initial stripe development was much later than last year, but about normal for this area.

In late May 2006, stripe rust was starting to increase on susceptible winter wheat entries in nurseries in the Palouse region of Eastern Washington.
Severities ranged from 1 to 10 percent with less than 1 percent of the plants infected. The stripe rust appeared one month later that last year in the Palouse region.

On 22 May 2006, stripe rust was found in a field in Franklin County, in southeastern Idaho, which is about 6 miles north of the Idaho-Utah border.
Pustules were just beginning to show on the flag leaves.

By mid-June 2006, stripe rust was widespread in eastern Pacific Northwest fields and plots. On 16 Jun 2006, 30 percent severities were reported on susceptible winter wheat entries and 10 percent on susceptible spring wheat entries in disease monitoring nurseries at the Pendleton Experiment Station in Oregon. In nurseries near Walla Walla, Washington stripe rust severities reached 100 percent on susceptible entries in both winter wheat and spring wheat nurseries. Stripe rust was found in commercial spring wheat fields in the Palouse area, where 10 percent of the plants were infected with severities less than 5 percent on lower leaves. The wet and cool conditions the first 3 weeks in June 2006 were conducive for rust production. By mid-July 2006, stripe rust development had slowed in Pacific Northwest fields because of the hot dry weather. In early-July 2006, 70-100 percent severities were reported on susceptible entries in plots where moisture was not limiting. Compared !
to last year, wheat stripe rust was lighter in the Pacific Northwest.

Utah. In early June 2006, light stripe rust was found on Garland wheat under irrigation in Logan, Utah. Stripe rust was not found in the dryland area in northwestern Utah. This is typical, since rust is rarely seen in Utah. Last year (2005) was an anomaly with quite severe stripe rust in Logan which started much earlier in the growing season. Prior to last year, the previous year that had significant stripe rust (or any rust) was 1993 (which was similar in temperature and moisture to 2005).

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

[There are 3 main rust diseases of the cereal crop plant wheat (bread wheat, _Triticum aestivum_ and durum wheat, _Triticum turgidum_), all caused by species of the fungus Puccinia: wheat stem rust (_P. graminis f.sp. tritici_), wheat leaf rust (_P. triticina_ aka _P. recondita f. sp. tritici_) and wheat stripe rust (_P. striiformis f. sp. tritici_).

Severe losses due to wheat stem rusts have abated in the USA since the 1960s due to effective resistance breeding. Severe losses are still a possibility with leaf rust. The USDA Cereal Disease Laboratory in St. Paul, MN publishes regular reports on cereal rusts in the USA during the crop season. Each report gives detailed state-by-state information, including a summary map, all in pdf file format (see link to main article). Information for rusts other than those that infect wheat is not included in this ProMED-mail posting but others are described in the full report.

This is the 10th and final report from the USDA Cereal Disease Laboratory for 2006. It is a detailed summary of the entire crop/disease season.

A common race of stem rust (QFCS) that has been found in the U.S. the past several years was also detected in 2006. It is relatively avirulent and the majority of the U.S. cultivars are resistant to it. Stem rust seems to be have been well managed by the use of resistant cultivars in 2006.

Leaf rust was held at bay in many parts of the USA by dry conditions and/or the use of fungicides. When southern states are dry this has the effect of reducing spore load for the south to north spore pathway. Highest levels of infection, especially on susceptible cultivars, appeared to be in mid-Atlantic and western states.

Stripe rust was noted in the Central Valley of California where there now appear to be strains capable of overcoming the cultivars commonly grown.

David Long indicated in this the final report for 2006 that he would be interested in any comments you might have on the Cereal Rust Bulletins.

Map:
Puccinia spore pathway
<http://www.ars.usda.gov/Main/docs.htm?docid=11301>
Wheat in USA
<http://www.nass.usda.gov/research/atlas02/Crops/Field%20Crops%
20Harvested/Wheat/All%20Wheat%20for%20Grain,%20Harvested%20Acres-chor.gif>

Pictures:
Wheat leaf rust
<http://www.cdl.umn.edu/nomenclature/inf_set.jpg>
Wheat stem rust
<http://www.gov.mb.ca/agriculture/crops/diseases/images/fac15s01.jpg>
Wheat stripe rust
<http://www.utextension.utk.edu/fieldCrops/wheat/Wheat_photos/Wheat_StripeRust.jpg>

Link:
<http://www.ars.usda.gov/Main/docs.htm?docid=9854>
- Mod.JAD]

[see also in the archive:
Cereal Rust Update - USA (09) 20060810.2243 Cereal Rust Update - USA (08) 20060713.1925 Cereal rust update - USA (07) 20060707.1861 Cereal rust update - USA (06) 20060601.1528 Cereal Rust Update - USA (05) 20060518.1406 Cereal Rust Update - USA (04) 20060502.1274 Cereal Rust Update - USA (03) 20060418.1144 Cereal Rust Update - USA (02) 20060404.1012 Cereal rust update - USA 20060322.0895]

RELATED RELEASE: Cereal rust update - USA