April 4, 2006
From: ProMED-mail<promed@promedmail.org>
Source: USDA Cereal Rust Bulletin 2006: Number 2 [edited]
<http://www.ars.usda.gov/Main/docs.htm?docid=9757>

Cereal Rust Bulletin, Report for 2006 No. 2

[As of April 4 2006]
- Wheat leaf rust is widespread throughout the southern U.S.
- Wheat stripe rust is at low levels in Texas but heavier in Louisiana.
- Wheat stem rust has not been reported in the U.S.

Wheat leaf rust

In late March 2006 in central Texas, commercial wheat fields had low levels of leaf rust infections and moderate levels in nurseries which had sufficient moisture for rust development due to recent rains. Susceptible cultivars growing in plots that had been irrigated in southern Texas nurseries had high severity levels of leaf rust. However, no leaf rust was found in southern Texas fields because of the drought conditions. In late March 2006, wheat plots in central Oklahoma had low levels of leaf rust. Wheat leaf rust has been found in fields and plots in the southern soft red winter wheat area from southern Georgia, southern Alabama to southern Arkansas. In late March 2006 in wheat plots at Alexandria, Louisiana, 20 percent leaf rust severities were observed on the lower leaves of susceptible cultivars. Some of the fields infected with rust have been sprayed for rust control in the southern U.S. Leaf rust will continue to increase rapidly with adequate moisture and warm weather, and
will provide rust inoculum for the wheat growing areas further north. In
late March 2006, the cultivar McCormick in southeastern North Carolina plots had low levels of leaf rust on lower leaves. This is an early observation for wheat leaf rust in North Carolina and is presumably due to over-wintering in that area.

Wheat stripe rust

In late March 2006, wheat fields and plots in southern and central Texas had low levels of wheat stripe rust infections (Fig. 2). When compared to
2005 at this time, stripe rust is much lighter throughout Texas. Weather conditions have not been favorable for rust development (limited moisture and few cool nights) in Texas. By the end of March 2006 no stripe rust had been reported in Oklahoma. In late March 2006, stripe rust was active in Louisiana and 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 2006 slowed stripe rust development. In late March 2006, stripe rust was light in fields in southern Arkansas.

--
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_). These are 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).

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 20060322.0895]