May 18, 2006
From: ProMED-mail<promed@promedmail.org>
Source: USDA Cereal Rust Bulletin 2006: Number 05, 16 May 2006 [edited] <http://www.ars.usda.gov/Main/docs.htm?docid=9757>


Wheat leaf rust is widespread at low to moderate levels in the US. Wheat stripe rust is at low levels in a few areas of the US.

Much of the wheat crop in the Central Plains is ahead of normal crop development and is in good condition. The winter wheat harvest has commenced from southern Texas to southern Georgia. Although much of the spring wheat crop has been planted, cool and wet weather has slowed initial growth.

Wheat stem rust

In late April 2006, wheat stem rust was found on 'Wintex' cultivar in Ellis County in north-central Texas. This was the first report of wheat stem rust found in Texas this year. From several collections made in Acadia county, Louisiana in April, race QFCS (with virulence to Sr5, 8a, 9a, 9d, 9g, 10, 17, and 21) was identified. This is a common race that has been found in the US the past several years. This race is relatively avirulent -- the majority of the US cultivars are resistant to QFCS.

Wheat leaf rust

From north-central Texas to south-central Kansas, wheat leaf rust infections are at low severity levels in fields and at moderate levels in plots. Wheat plots in Stillwater and Efaw Oklahoma have variable amounts of leaf rust severity with the highest between 25 and 40 per cent. In southern and central Oklahoma, wheat plants with scattered pustules were found, however the wheat in this area is close to maturity. In fields in south eastern and south central Kansas, flag and flag-1 leaves at full berry in mid-May, 10 per cent leaf rust severities could be found. In south-central Kansas plots of susceptible cultivars such as Jagalene had up to 60 per cent severities. The leaf rust infections in this area appear to have developed within the last 2 weeks. Drier-than-normal conditions in late April and early May slowed leaf rust development in the southern Great Plains. With the recent rainfall, leaf rust infections will increase and provide inoculum for the northern wheat-growing area. Low levels of leaf rust (10 per cent severity) were found in south western Missouri fields on
15 May 2006.

On 8 May, leaf rust infections that had overwintered were found on the lower leaves of winter wheat plants of the susceptible cultivar Cheyenne at the Rosemount Experiment Station in east-central Minnesota.

In early May, flag leaves of soft red winter wheat in central South Carolina plots had 5 per cent leaf rust severity. In the 2nd week in May, severe leaf rust infections were reported in plots at the Kinston station in east central North Carolina and in the wheat-breeding nursery at Warsaw in north east Virginia. From collections made in early March 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 survey (<http:// www.ars.usda.gov/mwa/cdl/>).

Wheat stripe rust

In early May, plots in Urbana, Illinois and in fields in east-central North Carolina had low levels of stripe rust incidence and severity. There have been no reports of wheat stripe rust in Kansas or Oklahoma. The drier and warmer-than-normal weather in March and April has slowed the increase and spread of stripe rust. In early May, stripe rust infections that overwintered were observed on susceptible winter wheat cultivars in the Gallatin Valley in south western Montana. The severity level was near 10 per cent.

--
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).

In this the 5th report for 2006, it is noted that wheat stem rust was found in late April 2006 in Texas, a first for that state this year. Other comments on the 3 main rusts of wheat seem to fall into the category of typical and expected. Any races that have been typed are ones also detected in recent years.

I have added a recent [14 May 2006] post on the Ug99 race of wheat stem rust that may have spread to Asia (Pakistan) from East Africa where it was first reported in 1999. Race Ug99 can infect and cause disease in many commonly grown "resistant" wheat lines and is considered a major threat to worldwide wheat production.

Maps:
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:
Wheat stem rust, strain Ug99 - Pakistan: susp., 1st report 20060514.1366 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]