A ProMED-mail post <http://www.promedmail.org>
ProMED-mail is a program of theInternational Society for Infectious Diseases <http://www.isid.org>
Date: Mon 16 Dec 2019
Source: North Queensland Register [abridged, edited] <https://www.northqueenslandregister.com.au/story/6546536/new-fungicide-resistant-strain-of-disease-found-on-yp/?cs=4751>
Fran Lopez-Ruiz, Centre for Crop and Disease Management (CCDM), said there had been samples of net form of net blotch (NFNB) coming in from South Australia's Yorke Peninsula with dual resistance against 2 of the most common modes of action in fungicide, the succinate dehydrogenase inhibitor (SDHI)-based products as well as some demethylation inhibitor (DMI) fungicides.
Testing found the strain of NFNB had mutated for resistance. The samples, collected from 2 paddocks a short distance apart, clearly showed high NFNB disease levels on the Spartacus variety of barley.
The DMI fungicide resistance mechanism is still being investigated, [but] Dr Lopez-Ruiz said it was known to be different to the DMI resistance mechanisms already reported in barley net blotches in Western Australia [ProMED-mail post http://promedmail.org/post/20180727.5931094]. The 1st cases of fungicide resistance [of net blotches] in Australia occurred in Tasmania.
[Byline: Gregor Heard]
--
Communicated by: ProMED-mail <promed@promedmail.org>
[Net blotch of barley is caused by the fungus _Pyrenophora teres_ and affects only domestic and wild barleys (_Hordeum_ spp.). The disease causes necrotic areas on leaves that reduce photosynthetic capacity and hence plant vigour, leading to yield losses of up to 20%. There are 2 types of the fungus, the net type caused by _P. t._ f. _teres_ and the spot type caused by _P. t._ f. _maculata_. The fungus survives between seasons on barley residues, volunteer barley plants, some grasses, and seed. Disease management includes cultural practices to remove pathogen reservoirs, fungicide applications, use of clean seed, and use of resistant cultivars.
Highly aggressive new strains of particularly the net form are emerging worldwide. Integrated disease management, including varying crops or crop cultivars in time and space, as well as rotating or mixing chemical classes of fungicides, is vital to extend the useful life of host resistances and agrochemical compounds.
In Australia, net blotch is considered an emerging threat to southern barley-producing areas (for example, see ProMED-mail post http://promedmail.org/post/20100323.0921). SDHI resistance has been reported in Europe, for example in the UK (ProMED-mail post http://promedmail.org/post/20140507.2457504), but not previously in Australia.
SDHI (succinate dehydrogenase inhibitor) 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. DMI (demethylation
inhibitor) fungicides were introduced in the 1970s.
Maps
Australia (with states):
<https://www.interkart.de/media/catalog/product/p/o/pod10th103_103_australia_physical.jpg>
Pictures
Net blotches on barley:
<http://agriculture.vic.gov.au/__data/assets/image/0005/227984/barley_2.jpg>
(net form),
<https://www.agric.wa.gov.au/sites/gateway/files/styles/original/public/Spot_type_net_blotch_mild_lesions.jpg?itok=ia7M9XDs>
(spot form),
<http://www.inra.fr/hyp3/images/6034311.jpg>,
<https://www.agric.wa.gov.au/sites/gateway/files/Barley%20NTNB%201_0.JPG>
and
<https://grdc.com.au/~/media/images/ground-cover/ground-cover-102-supplement/p05net-form-net-blotchma-copyjpg.jpg>
(affected field)
Links
Additional news story:
<https://www.farmweekly.com.au/story/6541531/new-dual-fungicide-resistance-in-barley/>
Information on net blotches of barley:
<http://www.inra.fr/hyp3/pathogene/6pyrter.htm>,
<http://agriculture.vic.gov.au/agriculture/pests-diseases-and-weeds/plant-diseases/grains-pulses-and-cereals/net-blotches-of-barley>,
<http://www.croppro.com.au/crop_disease_manual/ch02s18.php> and <http://www.ipm.ucdavis.edu/PMG/r730100311.html>
Fungicide resistant net blotch strains in Australia via:
<http://ccdm.com.au/frg/>
_P. teres_ taxonomy and synonyms:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=255071>
and
<http://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=255071>
Information on DMI fungicides:
<http://www.greenhousemag.com/article/gmpro-0610-dmi-fungicides-mode-of-action/>
and
<https://plant-pest-advisory.rutgers.edu/growers-guide-to-understanding-the-dmi-or-sbi-sterol-biosynthesis-inhibitor-fungicides-frac-code-3/>
Information on SDHI fungicides:
<https://www.frac.info/working-group/sdhi-fungicides/introduction-and-general-information>
and
<http://www.nzpps.org/journal/64/nzpp_641190.pdf>
CCDM
<http://ccdm.com.au/>
- Mod.DHA]
[See Also:
Leaf rust, barley - UK: (Scotland)
http://promedmail.org/post/20190502.6452058
2018
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Net blotch, barley - Australia: fungicide resistance (WA)
http://promedmail.org/post/20180727.5931094
Fungal diseases, barley - Ireland: population shifts
http://promedmail.org/post/20180510.5792118
2014
----
Fungal diseases, cereal crops - UK: SDHI resistance, alert
http://promedmail.org/post/20140507.2457504
2011
----
Barley diseases - India: (JK) survey
http://promedmail.org/post/20111201.3497
Fungal diseases, cereal crops - Ireland: alert
http://promedmail.org/post/20110525.1590
2010
----
Fungal diseases, cereals - Australia: alert
http://promedmail.org/post/20100825.2989
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
2008
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Cereal diseases - Australia, UK, USA
http://promedmail.org/post/20080707.2057
2004
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Barley net blotch, spot type - Uruguay: 1st report http://promedmail.org/post/20041130.3198]