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International Society for Infectious Diseases <http://www.isid.org>

Date: 10 March 2008
Source: Farmers Weekly Interactive [edited]
<www.fwi.co.uk/Articles/2008/03/10/109745/crop-watch-diseases-on-the-rise-as-gales-stop-fieldwork.html>

As wet and windy weather puts an abrupt stop to fieldwork, FWI's agronomists report increasing disease pressure in the run-up to the T0 [coleoptile tiller stage] fungicide timing.

"Cereal diseases have started to manifest themselves quite well and we are starting to see differences depending on variety and drilling date," Neil Potts said. Most wheat varieties in his part of Devon were showing good levels of septoria, with early drilled fields "going quite yellow with the disease". The only variety showing significantly less septoria was Gatsby, he noted.

Essex-based Andrew Blazey said there were increasing reports of brown and yellow rust and some forward wheats were carrying low levels of [powdery] mildew that would need treating at T0.

[Byline: Paul Spackman]

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[Cereal diseases of the septoria complex can be caused by the fungi _Mycosphaerella graminicola_ (previously _Septoria tritici_) and _Phaeosphaeria nodorum_. These pathogens cause blotches on both leaves and glumes. Leaf rust, also called brown rust, on wheat is caused by the fungus _Puccinia recondita_, and stripe (yellow) rust is caused by _P. striiformis_ var. _striiformis_. Both these rusts affect leaves reducing the photosynthetic potential of the plant.
Powdery mildew of wheat is caused by _Blumeria graminis_ and affects all aerial parts of the host.

These fungal pathogens have been reported from most cereal growing areas worldwide causing yield losses. New pathogen strains with increased virulence have been reported in several cases. Generally, fungi or their spores can be spread by infected plant material, wind and/or water, and mechanical means. Disease management for cereal hosts includes the use of resistant varieties, fungicide applications, and removal of inoculum sources.

Cereal disease management can be applied at key decision times (T0, T1, T2 and T3) to reflect the changing risk as the season unfolds. T reflects the growth stages referring to tillers present at a particular time: T0 refers to the coleoptile tiller, T1 to the tiller developing from the first leaf, etc. Early discovery of infection at any stage of the crop cycle is important so action can be taken to limit the spread of the pathogen as well as build-up of inoculum.

Maps of the UK:
<http://www.lib.utexas.edu/maps/europe/united_kingdom.gif>  and
<http://healthmap.org/promed?v=54.5,-2,5>

Pictures
Septoria diseases of wheat:
<http://www.omafra.gov.on.ca/french/crops/facts/90-008f3.jpg>  (leaf) and <http://www.omafra.gov.on.ca/english/crops/pub811/images/6septf2.jpg>  (ear) Wheat leaf rust:
<http://www.hgca.com/hgca/wde/IMAGES/brown%20rust1.JPG>
Wheat stripe rust:
<http://www.ars.usda.gov/Main/docs.htm?docid=9918&pf=1&cg_id=0>  and <http://utextension.tennessee.edu/fieldCrops/wheat/Wheat_photos/Wheat_StripeRust.jpg>

Powdery mildew on wheat:
<http://cropwatch.unl.edu/photos/cwphoto/crop04-9mildew1.jpg>  (leaf) and <http://www.hgca.com/hgca/wdmg/Gallery/mildew1.jpg>  (ear)

Links
Septoria, leaf rust, powdery mildew and other diseases of wheat:
<http://www.aces.edu/pubs/docs/A/ANR-0543/>
Information on septoria diseases:
<http://ipm.ppws.vt.edu/stromberg/smallgrain/biology/wgblotch.html>  and <http://www.cimmyt.org/Research/Wheat/pdf/septoria_ago99.pdf>
Information on wheat leaf rust:
<http://plant-disease.ippc.orst.edu/disease.cfm?RecordID=1138>
Information on wheat stripe rust:
<http://pnw-ag.wsu.edu/smallgrains/Stripe%20Rust.html>,
<http://www.ars.usda.gov/Main/docs.htm?docid=9918&pf=1&cg_id=0>  and
<http://www.oznet.k-state.edu/path-ext/factSheets/Wheat/Wheat%20Stripe%20Rust.asp>

Information on wheat powdery mildew:
<http://ohioline.osu.edu/ac-fact/0010.html>  and
<http://www.hgca.com/hgca/wde/diseases/Mildew/Milhost.html>
_M. graminicola_ taxonomy and synonyms:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=318177>
_P. nodorum_ taxonomy and synonyms:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=336201>
_P. recondita_ taxonomy and synonyms:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=145187>
_P. striiformis_ var. _striiformis_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=427989>
_B. graminis_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=309596>
Growth stages of cereals:
<http://www.grdc.com.au/GRDC/ResearchSummaries/CMAttachments/cropmonitoringv2.pdf>

- Mod.DHA]