A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
Date: Thu 28 Oct 2010
Source: UN Integrated Regional Information Networks (IRIN) News [edited] <http://www.irinnews.org/Report.aspx?ReportID=90907>
Wheat stem rust hits Rift Valley farmers
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Wheat stem rust Ug99 continues to threaten the livelihoods of hundreds of farmers in Kenya's Rift Valley region. Wet and misty conditions since November 2009 are making Ug99 even harder to control. Small-scale farmers who account for 80 percent of wheat growers are especially hard hit.
"Farmers this [2010] season are complaining that despite spraying their crop it has been affected by the rust," the agriculture extension officer in Njoro District (Rift Valley) said. "Before, we would spray the field twice but now we are being forced to apply the chemical up to 5 times," a farmer said.
According to a crop breeder with the Kenya Agricultural Research Institute (KARI), Peter Njau, farmers are embracing disease control.
Spraying fields when infestation is already too high or using the wrong products are some of the problems.
Of about 11 000 wheat varieties screened in 2005, less than 2 percent were found to have some resistance to Ug99. KARI is among the centres to develop Ug99-resistant wheat varieties and have produced 2 that are ready for trial.
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ProMED-mail
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[Wheat stem rust is caused by the fungus _Puccinia graminis_ f. sp. _tritici_. Overall yield losses of up to 80 percent are reported, but some fields are totally destroyed. New races are emerging, and the most dangerous at present is strain Ug99 (discovered in Uganda in 1999), which has overcome the major resistance gene Sr31 used in our current wheat varieties. Since then Ug99 has appeared in Kenya, Ethiopia, Sudan, Yemen, and Iran, and even more virulent variants of Ug99 able to overcome additional resistance genes have emerged including, for example, in Kenya's Rift Valley in 2009 (ProMED-mail post 20090312.1019). A new source of Ug99 strains was recently reported in South Africa opening up additional routes of transmission and increasing the threat in the southern hemisphere (ProMED-mail post 20100602.1834).
Stem rust spores are spread by wind and with infected straw, and some grasses or volunteer wheat may generate a "green bridge" providing inoculum for the next cropping season. Disease management may include fungicide applications, control of volunteer wheat, and resistant varieties if available. Breeding programmes have been set up in international cooperation (Delhi Declaration) to establish wheat varieties resistant to Ug99.
As mentioned in the report above, bad timing and unsuitable chemicals may well be a reason for the increased need of fungicides to control stem rust in Kenya. However, cereal rust strains with new fungicide resistances are emerging worldwide and the possibility of Ug99 strains developing additional fungicide resistances cannot be excluded. Such strains would be even more difficult to control.
Maps
Kenya:
<http://www.ogiek.org/photo-gallery/kenya-map-big.jpg> and
<http://healthmap.org/r/0f0I>
Kenya provinces:
<http://www.lib.utexas.edu/maps/africa/kenya_pol88.jpg>
Africa and Middle East:
<http://www.lib.utexas.edu/maps/africa/africa_pol97.jpg>
Pictures
Stem rust symptoms on wheat:
<http://www.ars.usda.gov/images/docs/9910_10104/stemrust_inset.jpg>,
<http://www.gov.mb.ca/agriculture/crops/diseases/images/fac15s01.jpg>, and
<http://www.irinnews.org/PhotoDetail.aspx?ImageId=201010281134020344> (Ug99)
Effects of Ug99 on resistant and susceptible wheat cultivars:
<http://www.irinnews.org/PhotoDetail.aspx?ImageId=201010281129340750>
Links
Information on wheat stem rust:
<http://www.ars.usda.gov/Main/docs.htm?docid=9910>
Information on Ug99:
<http://www.ars.usda.gov/Main/docs.htm?docid=14649>,
<http://www.pestalert.org/viewNewsAlert.cfm?naid=36> and
<http://www.agbioworld.org/newsletter_wm/index.php?caseid=archive&newsid=2686>
_P. graminis_ f.sp. _tritici_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=455607>
Global Rust Initiative:
<http://www.globalrust.org/>
KARI:
<http://www.kari.org/>. - Mod.DHA]
[see also:
Wheat stem rust, Ug99 group: new races 20100602.1834
2009
----
Stem rust, wheat - India: new strain 20090717.2548
Wheat stem rust, strain Ug99: resistance breeding 20090326.1168
Wheat rusts - Kenya, India, Australia 20090312.1019
2008
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Wheat stem rust Ug99 - Australia ex Ethiopia: interception 20081203.3807
Wheat stem rust, strain Ug99 - multicountry: update 20081120.3660
Wheat stem rust, strain Ug99 - Iran: 1st rep, alert 20080307.0925
2007
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Wheat stem rust, strain Ug99 - Kenya: new variant 20071217.4054
Wheat stem rust, strain Ug99 - multistate: resistance screening 20071208.3957
Barley yellow dwarf virus & stem rust, cereals - Kenya 20070705.2132
Wheat stem rust, strain Ug99 - Yemen (02): government response 20070430.1399
Wheat stem rust, spread: FAO, Global Rust Initiative 20070414.1241
Wheat stem rust, strain Ug99 - Yemen: 1st report 20070117.0229
2006
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Wheat stem rust, strain Ug99 - Pakistan: susp., 1st report 20060514.1366
Stem rust, wheat - multicountry: new strains 20060406.1039
2005
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Wheat stem rust, Ug99, new strain - East Africa 20050928.2849
Wheat stem rust, new strain - Uganda 20050912.2698
2002
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Wheat stem rust fungus, new virulence genes - So Afr 20020814.5049
2000
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Wheat stem rust in resistant wheat lines - Uganda 20000702.1092
1999
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Stem-rust fungus, mutant, wheat - Uganda 19990519.0812]
Topics
Species
