Date: August 5 2006
From: ProMED-mail <promed@promedmail.org>
Source: USDA Cereal Rust Bulletin 2006: Number 09, 18 Jul 2006 [edited] <http://www.ars.usda.gov/Main/docs.htm?docid=9757>


The small grain harvest has commenced from southwestern New York to northern South Dakota. Drought-like conditions are common in the most of the northern small grain area, which will hasten crop maturity.

Wheat stem rust

Wheat stem rust has been reported on susceptible spring wheat in the northern plains. In mid-July 2006, trace to 10 percent severities of wheat stem rust were observed on the susceptible spring wheat cultivar Baart in southern and west central Minnesota and east central North Dakota. All of the current spring wheat cultivars are resistant to the prevalent U.S. race population. Earlier in the year, there were few reports of wheat stem rust in the southern U.S.
grain growing area. 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 is present in low to high severity levels on spring wheat cultivars in the northern plains. In 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 early July 2006, high levels of leaf rust severity were found on 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. Many wheat fields have been sprayed with fungicide to prevent losses due to rust and scab. Hot dry weather combined with severe leaf rust infections will kill the flag leaves of spring wheat. In early July, low levels of leaf rust were found in winter wheat plots at Ithaca, New York. In mid-July, leaf rust was very light in experimental plots at Pullman and Mt. Vernon, Washington. No rust was found in grower's fields.

Wheat stripe rust

In mid-July, hot dry weather had stopped development of stripe rust on spring wheat in the northern Great Plains. By mid-July, stripe rust development has slowed in Pacific Northwest fields because of the hot dry weather. In early July, 70-100 percent severities were reported on susceptible entries in plots where moisture was not limiting. Compared to last year, wheat stripe rust is lighter in the Pacific Northwest.

--
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 report for mid July 2006 deals mostly with the more northerly production areas in the USA and confirms that rusts are present on susceptible lines and that fungicide treatments are still needed for some commonly grown lines that do not have robust resistance.

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 (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]