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: Mon 7 Dec 2015
Source: Farmers Weekly [edited]
<https://www.fwi.co.uk/arable/sdhi-fungicide-resistant-septoria-found-in-irish-fields.htm>
Fungicide-resistant septoria in Irish fields
Strains of the yield-robbing wheat disease septoria with target-site resistance to SDHI [succinate dehydrogenase inhibitor] fungicides have been discovered in southern Ireland [by] Irish advisory body Teagasc [Agriculture and Food Development Authority] in samples taken at the end of the 2015 season.
This is the 1st time they have been detected in the field and although at a low frequency, it is a worrying development, particularly as the efficacy of other septoria-controlling fungicides is already much reduced.
John Spink, Teagasc, [said] these strains could quickly spread and increase as a proportion of the population and would leave Irish growers with little means of controlling the wet weather disease. "If these strains became widespread, we would stop growing wheat. It would cease to be economic," he explained.
Due to the low frequency of the resistant strains in Ireland, growers there are still likely to get good control from SDHI fungicides during the 2016 season. However, Teagasc are warning of the importance of using good anti-resistance strategies to slow any rise in frequency of the resistant strains.
Mr Spink warned that in Ireland a more robust disease monitoring scheme is in place compared with the UK, so there could already be resistant isolates that side of the Irish Sea that haven't been picked up. "If fungicides aren't used in sensible mixes and doses, these isolates will be rapidly selected."
[Byline: Adam Clarke]
--
Communicated by: ProMED-mail <promed@promedmail.org>
[Septoria leaf blotch of cereals is caused by fungi in the septoria species complex which includes _Zymoseptoria tritici_ (previously _Septoria tritici_) , _Mycosphaerella graminicola_ and _Phaeosphaeria nodorum_ (previously _Stagonospora nodorum_). They affect mainly wheat, but also barley and oats and occasionally rye and some grass species. Symptoms on wheat and barley are very similar and may occur at any time during the growth of the plant and on any portion of the plant. They include blotches on both leaves and glumes which reduce the photosynthetic ability of the host. Up to 50 per cent yield losses have been reported on susceptible varieties.
Spores can be spread by infected plant material, wind, water (rain splash), and mechanical means. The pathogens can overwinter on crop debris and on autumn sown crops or volunteers. Disease management includes fungicide treatments aimed at preventing the disease becoming established on the upper 3 leaves of the crop canopy, removal of inoculum sources and use of resistant varieties. Septoria is considered the most important foliar disease of winter wheat in the UK and other parts of Europe where it has evolved high levels of resistance to many fungicides. After the cereal rusts, the disease is considered the most important challenge to plant breeders (see ProMED-mail post http://promedmail.org/post/20120831.1274190) and a threat to food security worldwide.
While SDHI fungicides are not new, their previous limited use meant that resistance under commercial conditions remained limited to a few pathogens and crops. A "2nd generation" of SDHIs is currently being used to combat fungal diseases that have developed resistance to other groups of fungicides.
In the UK, SDHI resistance was confirmed for the 1st time in 2014 in barley net blotch (_Pyrenophora teres_) and an alert was issued for the possible emergence of SDHI resistance of septoria pathogens (ProMED-mail post http://promedmail.org/post/20140507.2457504).
Maps
Ireland:
<http://www.vidiani.com/maps/maps_of_europe/maps_of_ireland/general_map_of_ireland.jpg>
and
<http://healthmap.org/promed/p/39>
Irish counties:
<http://www.spirited-ireland.net/map/_counties/ireland_map22.gif>
Europe, overview:
<http://www.youreuropemap.com/europe_map_political.gif>
Pictures
Wheat crop affected by septoria:
<https://www.agric.wa.gov.au/sites/gateway/files/styles/original/public/septoria_nodorum_withered_leaves.jpg?itok=-ZWZPjFM>
Septoria leaf symptoms:
<http://ipm.illinois.edu/bulletin/photos/septoria_wheat.jpg>,
<http://www.abgenternasyonel.com/images/icerik/septoria%20tritici.jpg>,
and
<http://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Article%20Images/SeptoriaTriticiBlotch01.jpg>
Septoria symptoms on wheat ear:
<http://www.omafra.gov.on.ca/english/crops/pub811/images/6septf2.jpg>
Septoria on resistant and susceptible wheat varieties:
<http://www.fao.org/docrep/006/y4011e/y4011e1d.jpg>
Septoria diseases and pathogens, photo gallery:
<http://www.forestryimages.org/browse/subimages.cfm?sub=9457>
Links
Additional news story:
<http://www.farmersjournal.ie/sdhi-defences-breach-confirmed-195409/>
Information on septoria diseases:
<http://www.agroatlas.ru/en/content/diseases/Tritici/Tritici_Septoria_tritici/>,
<http://www.agroatlas.ru/en/content/diseases/Tritici/Tritici_Septoria_nodorum/>,
<http://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/Septoria.aspx>,
and
<http://cereals.ahdb.org.uk/cereal-disease-encyclopedia/diseases/septoria-leaf-blotch.aspx>
(incl. life cycle)
Taxonomy of all fungal species via:
<http://www.indexfungorum.org/Names/Names.asp>
Information on SDHI fungicides:
<http://www.nzpps.org/journal/64/nzpp_641190.pdf>
Teagasc:
<http://www.teagasc.ie>
- Mod.DHA]
[See Also:
Septoria blotch, wheat - Ethiopia: survey of incidence
http://promedmail.org/post/20151018.3725790
Septoria blotch, wheat - Europe: fungicide resistance
http://promedmail.org/post/20150619.3450044
2014
----
Fungal diseases, cereal crops - UK: SDHI resistance, alert
http://promedmail.org/post/20140507.2457504
Septoria blotch, wheat - New Zealand: new strains, strobilurin resistance http://promedmail.org/post/20140417.2410219
Septoria, wheat - Australia: new strains, alert
http://promedmail.org/post/20140313.2329774
2011
----
Fungal diseases, cereal crops - Ireland: alert
http://promedmail.org/post/20110525.1590
2010
----
Fungal diseases, cereals - Australia: alert
http://promedmail.org/post/20100825.2989
Fusarium head blight & stagonospora, wheat - USA: (OH)
http://promedmail.org/post/20100708.2277
Septoria, wheat & barley - France: (BN)
http://promedmail.org/post/20100517.1608
Fungal diseases, cereals - Germany: (SN)
http://promedmail.org/post/20100428.1370
Net blotch, barley - Australia: (SA) new strains, alert
http://promedmail.org/post/20100323.0921
2009
----
Fungal diseases, cereal crops - China, Ireland
http://promedmail.org/post/20090528.1983
Fungal diseases, cereal crops - France, Germany
http://promedmail.org/post/20090504.1668
Fungal diseases, barley - UK http://promedmail.org/post/20090123.0291
and older items in the archives]
Topics
Species
