ProMED
http://www.promedmail.org

Source: FarmingUK [abridged, edited]
https://www.farminguk.com/news/septoria-warning-as-high-levels-of-latent-disease-found_58174.html

A septoria warning has been issued to UK growers. Septoria pressure in wheat crops is expected to build in the coming weeks. Laboratory analysis of samples has shown high levels of latent septoria, which indicates disease pressure could be greater than expected.

Microgenetics' rapid test for septoria indicates the level of infection. [They] said they had not been surprised by the number of positive samples sent in from fields across England and Wales. They had detected latent septoria in over 400 samples sent to their laboratory. "Many of the positive samples come from varieties which do not have a strong disease profile, and where growers might expect septoria, even if it was not visible. We have also had positive samples from varieties which have excellent septoria ratings, which demonstrates the importance of testing before deciding on [fungicide] choice and dose.

Univoq fungicide was approved in the UK last month [April 2021] and offers control on all septoria strains. The product is the 1st new target site for septoria control registered in the UK for 15 years.
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Communicated by:
ProMED
<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, oats, occasionally rye, as well as some grass species. Symptoms on wheat and barley are very similar, they may occur at any time during the growth cycle and on any portion of the plant. They include blotches on both leaves and glumes, which reduce the photosynthetic ability of the host. Disease development is favoured by humid conditions. Up to 50 percent 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 (where it would affect the ears most), removal of inoculum sources, and use of resistant varieties. After the cereal rusts, the septoria is considered the most important challenge to plant breeders (see ProMED post 20120831.1274190) and a threat to food security worldwide.

Pathogen strains with high levels of resistance to many fungicides are emerging, for example, in the UK and other parts of Europe (ProMED post 20160516.4225677), as well as Australia and New Zealand (ProMED posts 20161031.4598540 and 20140417.2410219). With high disease levels recently reported in the UK on winter wheat cultivars currently considered to be resistant to the pathogens (ProMED post 20190218.6322156), host resistance break down may also be a possibility.

In the UK and elsewhere, the number of fungicides available for septoria control has been decreasing over recent years, due to emergence of resistant fungal strains as well as withdrawal of products for environmental reasons (e.g. ProMED-mail post 20210223.8207530). Univoc is a broad-spectrum fungicide based on a new mode of action against major foliar wheat diseases [see link below]. Its introduction is also expected to extend the useful life of other still available fungicides by reducing the risk of pathogen strains resistant to either of the chemical groups to develop. Rotating or mixing chemical classes of fungicides is also vital to extend the useful life of host resistance genes in crop varieties.

Maps
UK:
http://healthmap.org/promed/p/40,
https://www.worldometers.info/img/maps/unitedkingdom_physical_map.gif, and
https://tinyurl.com/ml5ggkx (regions and counties)

Pictures
Septoria leaf symptoms:
http://ipm.illinois.edu/bulletin/photos/septoria_wheat.jpg and
https://www.farminguk.com/images/news/44568_2.jpg
Wheat crops affected by septoria:
https://s0.geograph.org.uk/geophotos/02/98/84/2988496_24261618.jpg and
https://www.agric.wa.gov.au/sites/gateway/files/styles/original/public/septoria_nodorum_withered_leaves.jpg
Septoria diseases and pathogens, photo gallery:
http://www.forestryimages.org/browse/subimages.cfm?sub=9457

Links
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/,
https://www.apsnet.org/edcenter/disandpath/fungalasco/pdlessons/Pages/Septoria.aspx,
https://cropscience.bayer.co.uk/threats/diseases/wheat-diseases/septoria-tritici-in-wheat/,
https://cropprotectionnetwork.org/resources/articles/diseases/septoria-tritici-blotch-of-wheat,
https://ipm.ca.uky.edu/content/septoria-leaf-blotch-complex-wheat, and
https://agriculture.vic.gov.au/biosecurity/plant-diseases/grain-pulses-and-cereal-diseases/septoria-tritici-blotch-of-wheat
Taxonomy of fungal species via:
http://www.indexfungorum.org/Names/Names.asp
Information on new Univoq fungicide:
https://ahdb.org.uk/news/fungicide-performance-data-for-new-wheat-product-univoq-released
History and review of agricultural fungicides:
https://www.apsnet.org/edcenter/apsnetfeatures/Pages/Fungicides.aspx
Microgenetics:
https://www.microgenetics.co.uk/
- Mod.DHA]