June 1, 2006
From: ProMED-mail<promed@promedmail.org>
Source: USDA Cereal Rust Bulletin 2006: Number 06, 30 May 2006 [edited] <http://www.ars.usda.gov/Main/docs.htm?docid=9757>


The small grain harvest is underway from Georgia to Oklahoma. Winter wheat is at normal crop development stage in the central plains. Most of the spring grain in the northern plains is at average maturity.

Wheat stem rust in southwestern Georgia

In mid-May, light wheat stem rust was found in southwestern Georgia plots at Plains. To date wheat stem rust has been reported at sites in southwestern Georgia, north-central Texas and southwestern Louisiana.

Wheat leaf rust in the northern Great Plains

In mid-May, light leaf rust was found in fields and plots in central Kansas. During the 3rd week in May, 1 percent severities were observed on flag leaves of susceptible cultivars in northeastern Kansas plots. In mid-May, light leaf rust was found on lower leaves of wheat plants in research plots in central Nebraska. Hot dry weather slowed leaf rust development in the southern and central Great Plains the last part of May. On May 26, 5 percent severities were found on flag-2 leaves in susceptible winter wheat plots in Dakota County in east-central Minnesota. In mid-May, 60 percent severities were found in susceptible soft red winter wheat cultivars in northern Alabama plots. By mid-May, 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, which may result in significant losses in the area. This year wheat leaf rust development is greater than normal in the Mid-Atlantic states. In mid-May, leaf rust severities up to 80 percent were observed in susceptible cultivar plots in Kern county and Madera County, California late in the season.

Wheat stripe rust is light in the Great Plains

On 22 May, traces of wheat stripe rust were found on the flag leaves of susceptible cultivars in plots at Manhattan, Kansas. On May 26, 10 percent stripe rust severities were found on flag leaves of susceptible winter wheat in east central Minnesota plots. At both of these locations spores were deposited with rain showers in the past 2 weeks. In late May, hot dry weather slowed rust development in these areas. In mid-May, wheat stripe rust was found in Limestone county plots in north-central Alabama. In mid-May, hotspots of stripe rust were found in wheat plots in the eastern shore of Virginia and Maryland. Heavy stripe rust was reported in commercial fields in the Albermarle/Pamilico Sounds region in east central North Carolina in early May. By late May, 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. On 22 May, 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 and entire plants had small chlorotic areas that could develop into a severe outbreak.

--
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.

In this the 6th report for 2006, most observations are as expected, and deal with observations of disease in susceptible lines, often in experimental plots. It is noted that wheat leaf rust development is greater than normal in the Mid-Atlantic states in 2006. It is also noted that 2 wheat cultivars commonly grown in California, Summit and Blanca Grande, are now both fully susceptible to the races of stripe rust that occur in that state. If conditions in California are favorable to stripe rust in future years then alternate varieties may need to be grown.

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>

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

[see also in the archive:
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]