A
ProMED-mail post
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International Society for Infectious Diseases
Cereal rust update - USA
Date: 13 July 2006
From: ProMED-mail <promed@promedmail.org>
Source: USDA Cereal Rust Bulletin 2006: Number 08, 26 Jun
2006 [edited] <http://www.ars.usda.gov/Main/docs.htm?docid=9757>
The small grain harvest has commenced from eastern Pennsylvania
to southern South Dakota. Winter wheat is generally in good to
poor condition and ahead of normal maturity throughout most of
the U.S. Spring-planted small grain crops are ahead of normal
maturity throughout much of the area.
Wheat stem rust
There have been no further reports of wheat stem rust since late
May, when rust was reported in Baton Rouge, Louisiana and
Kinston, North Carolina soft red winter wheat plots. 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 in the upper Midwest is at high severities on
susceptible winter wheat and is increasing on susceptible spring
wheat. In late June, plots of susceptible winter wheat cultivars
such as Jagalene, 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, spring wheat had leaf rust severities of trace to
1 percent on lower leaves in southern Minnesota and North Dakota
fields. Susceptible spring wheat cultivars in southern Minnesota
plots had 20 percent rust severities with most infections on the
lower leaves. This year leaf rust is 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. Drier than normal
conditions in May and June in many areas of the northern Great
Plains has further slowed rust development. Some of the spring
wheat cultivars currently grown have less effective resistance
to leaf rust than those commonly grown 10-15 years ago. Many of
the wheat fields in the spring wheat region will be treated with
fungicide, which will prevent losses due to leaf rust. More leaf
rust was found this year than last year in Ohio. By mid-June,
leaf rust was severe on the upper leaves of susceptible
cultivars throughout the northern wheat growing areas of Ohio.
The 1st report of leaf rust in Ohio was during the 2nd week in
May in south central Ohio, where the rust may have overwintered.
Moisture conditions throughout this area have been conducive for
rust development. As of late June, no wheat leaf rust had been
in found New York.
Wheat stripe rust
Wheat stripe rust is widespread in the Pacific Northwest and has
stopped throughout the northern plains wheat-growing area. By
the 3rd week in June, traces of stripe rust were found on a few
winter wheat cultivars in east central South Dakota and
east-central Minnesota plots (Fig. 2). Hot weather has stopped
rust production in these plots. The only report of stripe rust
this year in Ohio was in a wheat breeding line. In 2005, stripe
rust was found at a number of locations in Ohio. By mid-June,
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
were conducive for rust production. Cool and wet weather the
first half of June have been favorable to stripe rust
development in Montana winter wheat. In central and east central
Montana 15 000 - 20 000 acres of winter wheat have been sprayed
with fungicides. There have been sporadic reports of stripe rust
spreading to spring wheat, but the severity has been low. It has
been dry and warm since the middle of June and stripe rust
development has slowed considerably during the latter part of
June. In mid-June, wheat stripe foci of 60-80 percent severity
were observed in winter wheat nursery plots at Winnipeg,
Manitoba, Canada. Infections were noted on lower leaves,
indicating that overwintering may have occurred. Very mild
winter conditions with adequate snow cover occurred in
2005-2006, and spring temperatures were near normal, which would
have been favorable for stripe rust infection.
--
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, Minnesota 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 late June 2006 confirms that rust is present on
susceptible lines and that fungicide treatments are still needed
for some commonly grown lines that do not have robust
resistance. Climatic reasons are presented to explain lower
amounts of leaf rust inoculum than in previous years.
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 (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] |