A
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International Society for Infectious Diseases
A ProMED-mail post
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ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
Date: 23 June, 2008
Source:
Daily Liberal [edited]
<http://dubbo.yourguide.com.au/news/local/news/environment/disease-of-wheat-a-threat-to-harvest/794922.aspx>
Disease of wheat a threat to harvest
Disease has joined drought in threatening the chances of central
west New South Wales farmers in 2008.
Leaf rust has been found in a wheat sample from Dunedoo,
prompting the Grains Research and Development Corporation (GRDC)
to call for action. "This issue should not be taken lightly as
it has the potential to devastate the Australian grains
industry," GRDC manager of crop protection Rohan Rainbow said.
University of Sydney plant pathologist Colin Wellings says
growers should plan for control strategies. "One sample from
Marombi wheat at Dunedoo was infected with leaf rust and a
sample of stripe rust was taken from Tobruk triticale at Young,"
he said. "This is a notably early occurrence for rust diseases
in commercial fields."
Dr Wellings said a wet summer had contributed to survival of
rust pathogens and, depending on seasonal conditions for crop
growth in 2008, he expected rusts would be widespread and
potentially damaging.
"Crops now well established from early seeding will need to be
inspected immediately," he said. Foliar fungicides combined with
strategic grazing should be considered, he said, with due
attention paid to withholding periods.
Growers support the Australian Cereal Rust Control Program
through the GRDC. Dr Rainbow said current GRDC-supported trials
showed the use of fungicides at seeding for main season and
late-planted wheat provided early crop protection. "Selection of
rust-resistant varieties, teamed with control of the green
bridge of volunteer plants over summer and strategic fungicide
use, are the 3 clear strategies we need growers to take on
board," he said
--
Communicated by:
ProMED-mail
<promed@promedmail.org>
[Leaf rust, also called brown rust, on wheat is caused by the
fungus _Puccinia recondita_. It reduces the photosynthetic
potential of the plant and can cause serious yield losses of
over 40 percent in individual fields. Symptoms include brick-red
pustules on leaves, stems, and later on heads. As the crop
ripens, spores are produced.
Infection of the host can occur in as little as 4 hours in
favourable conditions. Epidemic severity increases exponentially
over time and may appear to "explode" suddenly during favourable
weather. It is not soil-borne and spores are spread by wind and
mechanical means.
Wheat stripe rust (also called yellow rust) is caused by the
fungus _Puccinia striiformis_ var. _striiformis_ and occurs
worldwide mostly in cooler climates. It causes yellow leaf
stripes, stunting of plants, and reduced grain number and size
on developing heads. Yield losses may vary from 40 up to 100
percent. It affects wheat, some barley varieties, triticale
(wheat/rye hybrids), and a number of grass species. Spores are
wind dispersed in several cycles during the cropping season.
Since the fungus interferes with seed development, infection
early in the crop cycle is more damaging than infection after
seed fill has concluded.
Both rust fungi need living tissue to survive between seasons
and cannot survive on seed, stubble, or in soil. Volunteer
wheat, barley, and certain wild grasses may generate a "green
bridge" providing inoculum to infect new crops. Disease
management relies mainly on timely fungicide applications,
choice of crop cultivars and control of volunteer wheat plants.
Early discovery of infection at any stage of the crop cycle is
important so action can be taken to limit the spread of the
pathogens as well as build-up of inoculum.
The emergence of new strains of cereal rusts is being monitored
in Australia. Surveys of rust pathotypes in 2003, for example,
identified 6 pathotypes each of stripe and leaf rust as well as
9 pathotypes of wheat stem rust (_P. graminis_).
Maps
Australia:
<http://www.ga.gov.au/image_cache/GA4073.jpg>
and <http://healthmap.org/promed?v=-25.7,134.5,4>
NSW:
<http://www.ozhorizons.com.au/nsw/map.htm>
Pictures
Leaf rust on wheat:
<http://www.hgca.com/hgca/wde/IMAGES/brown%20rust1.JPG>,
<http://www.hgca.com/hgca/wde/diseases/Brown%20rust/brstd.html>,
and <http://www.hgca.com/hgca/wde/diseases/Brown%20rust/brstaxil.html>
Stripe rust leaf symptoms on wheat:
<http://www.ars.usda.gov/Main/docs.htm?docid=9918&pf=1&cg_id=0>
and <http://utextension.tennessee.edu/fieldCrops/wheat/Wheat_photos/Wheat_StripeRust.jpg>
Links
Information on wheat leaf rust:
<http://plant-disease.ippc.orst.edu/disease.cfm?RecordID=1138>,
<http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp>,
and
<http://www.hgca.com/hgca/wde/diseases/Brown%20rust/Brhost.html>
_P. recondita_ taxonomy and synonyms:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=145187>
Information on wheat stripe rust:
<http://www.hgca.com/hgca/wde/diseases/Yellow%20rust/Yrhost.html>,
<http://www.ars.usda.gov/Main/docs.htm?docid=9918&pf=1&cg_id=0>,
and <http://www.oznet.k-state.edu/path-ext/factSheets/Wheat/Wheat%20Stripe%20Rust.asp>
Stripe rust management:
<http://www.grdc.com.au/uploads/documents/striperustmgt.pdf>
_P. striiformis_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=427989>
GRDC:
<http://www.grdc.com.au>.
- Mod.DHA]
[see also in
the
archive:
Leaf rust, wheat - USA: (KS, OK) 20080519.1665 Fungal diseases,
cereals - UK, Ireland: update 20080428.1460 Fungal diseases,
wheat - Canada, USA 20080427.1454 Wheat stripe rust, oilseed
rape sclerotinia - China 20080408.1297 Fungal pathogens, wheat -
UK (England) 20080319.1055 Stripe rust, wheat - Denmark: new
strains 20080211.0542
2007
----
Stripe rust, wheat - Australia (SA): new strain 20070921.3135
Stripe rust, wheat & wheat streak mosaic - Australia (SA, WA)
20070830.2860 Fungal diseases, wheat & pulses - Australia (SA)
20070821.2729 Stripe rust, wheat - USA, Australia 20070614.1950
Fungal pathogens, wheat - United Kingdom: new races
20070523.1652 Rust diseases, bean & wheat - UK: alert
20070512.1515
2006
----
Leaf rust, wheat - Russia (Irkutsk) 20060815.2287
2005
----
Leaf rust, wheat, resistance change - India 20051201.3462 Stripe
rust, wheat - Australia 20051031.3173 Leaf rust, Septoria spp.,
wheat - Kazakhstan: corr. 20050825.2509 Leaf rust, Septoria
spp., wheat - Kazakhstan 20050823.2488]
2004
----
Wheat stripe rust - Australia (NSW) 20040928.2683 Wheat stripe
rust - Australia (NSW): alert 20040810.2215
2003
----
Wheat stripe rust, new strains - Australia (SA) 20030930.2465
Wheat stripe rust - Australia (WA) 20030624.1553
2002
----
Wheat stripe rust - Australia (Western): alert 20020831.5198] |
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