A ProMED-mail post
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Date: Tue 15 Apr 2014
Source: NZ Farmer [edited]
Confirmation that New Zealand wheat has developed resistance to fungicides controlling Septoria tritici blotch (STB), or speckled leaf blotch, is another blow for wheat growers.
The Foundation for Arable Research (FAR) confirmed the disease had developed resistance to a fungicide group which had been most effective in controlling it, strobilurins (incl. azoxystrobin, pyraclostrobin, fluoxastrobin, picoxystrobin, trifloxystrobin). FAR said the disease had been increasing in severity for the past 4 years.
Federated Farmers' David Clark said he had already seen losses of 2 or
3 tonnes a hectare this [2014] season [and] expects [the disease] to spread throughout the industry. He said the industry was struggling to find an alternative fungicide and wheat growers should look hard at growing cultivars that had better resistance to the disease.
Federated Farmers' Colin Hurst said [the] findings were "quite a shock really. We'll obviously focus on some of the newer resistant varieties to keep the yields up."
FAR's Nick Poole said growers were being advised to rethink disease management. "There will have to be greater emphasis on integrated disease management (IDM)." He said the [strobilurin] resistance also highlighted the importance of the new succinate dehydrogenase inhibitor (SDHI) fungicides, which were unaffected by strobilurin resistance. The industry would need to protect the activity of fungicides by not exceeding the recommended maximum applications.
[Byline: Rob Tipa]
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Communicated by:
ProMED-mail
[Cereal diseases of the septoria complex are caused by the fungi _Mycosphaerella graminicola_ (previously _Septoria tritici_) 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 percent yield losses have been reported on susceptible varieties. Septoria is considered the most important foliar disease of winter wheat in the UK and other parts of Europe.
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.
Earlier in 2014, septoria developing fungicide resistance was reported for the 1st time in Australia (ProMED-mail post 20140313.2329774). It is not clear whether the 2 occurrences in the region are connected.
Strobilurins are strongly antifungal agents produced by fungi. Being derived from natural products, they are considered environmentally safe and are used against most major fungal crop diseases. Therefore, pathogen resistance is of major concern to many primary industries worldwide. Rotating or mixing chemical classes of fungicides are used to extend the useful life of the compounds.
Maps
New Zealand:
NZ regions:
Pictures
Wheat crop affected by septoria:
Septoria leaf symptoms:
and
Septoria symptoms on wheat ear:
Septoria on resistant and susceptible wheat varieties:
Septoria diseases and pathogens, photo gallery:
Links
Information on septoria diseases:
and
Septoria life cycle:
_M. graminicola_ taxonomy and synonyms:
_P. nodorum_ taxonomy and synonyms:
Information on strobilurins:
- Mod.DHA
A HealthMap/ProMED-mail map can be accessed at:
[See Also:
Septoria, wheat - Australia: new strains, alert 20140313.2329774
2011
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Fungal diseases, cereal crops - Ireland: alert 20110525.1590
2010
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Fusarium head blight & stagonospora, wheat - USA: (OH) 20100708.2277 Septoria, wheat & barley - France: (BN) 20100517.1608 Fungal diseases, cereals - Germany: (SN) 20100428.1370
2009
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Fungal diseases, cereal crops - China, Ireland 20090528.1983 Fungal diseases, cereal crops - France, Germany 20090504.1668
2008
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Cereal diseases - Australia, UK, USA 20080707.2057 Fungal diseases, cereals - UK, Ireland: update 20080428.1460 Fungal pathogens, wheat - UK (England) 20080319.1055
2006
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Cereal diseases, fungal - Russia, Kazakhstan 20060816.2298
2005
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Topics
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