.

Date: August 10, 2007
Source: Farmers Guardian [edited]
<http://www.farmersguardian.com/story.asp?sectioncode=19&storycode=11998>

High _Fusarium_ levels in some wheat regions

Latest wheat ear disease monitoring results have highlighted regional variations in levels of the toxin-forming ear blight _Fusarium graminearum_, says the HGCA [Home Grown Cereals Association].
_Fusarium_ head blight (FHB) levels in wheat crops are high this year [2007], although the survey results suggest that this is largely caused by non-toxin producing species.

However, 30 percent of samples were found to contain the toxin-forming _Fusarium graminearum_, with fields in the East Midlands and the south west of England being particularly hard hit.
Levels of _F. graminearum_ in these regions are 3 times higher than in other parts of the country. Farmers are warned that lodged crops are even more at risk from having raised mycotoxin levels and harvesting should be carried out as soon as possible.

All the samples in the Defra [Department for Environment, Food and Rural Affairs]/HGCA-funded winter wheat survey, underpinning CropMonitor [HGCA disease level information website], have now been assessed and more than 90 percent showed symptoms of FHB. This level is by far the highest seen since ear assessments began in 1986; the previous high was recorded in 1998 when 61 percent of samples showed FHB symptoms. The overall profile of species isolated is similar to that seen in 1998.

Results indicate that the predominant species present are _Microdochium_ species -- _M. nivale_ and _M. majus_ -- both of which are non-toxin producers. These species were isolated from 75 percent of samples, with an average of 7 percent ears affected per sample.

_Fusarium poae_ was the next most frequently isolated species present in 58 percent of samples, with an average of 3 percent of ears affected.

As levels of deoxynivalenol (DON) were low in 1998, it seems likely that overall DON contamination of grain this year [2007] is also likely to be low, says the HGCA. According to Roger Williams, HGCA's assistant director of research, growers should not assume that fusarium mycotoxins will be a widespread problem. However, he says that toxin levels may be raised if crops are lodged or harvest is delayed. As levels of _Microdochium_ species are high, there is an increased need for seed testing and subsequently for appropriate seed treatment to control _Microdochium_ species. Growers can monitor the latest information on the risk of _Fusarium_ mycotoxins at:
<http://www.cropmonitor.co.uk>.

Nickerson [a European plant breeding and seed development company] plant pathologist Paul Fenwick says the UK has the ideal climate for _Fusarium_. "The risk is heightened in mixed cropping areas where maize is grown as the maize trash carries the inoculum over into the following wheat. The warning sign is showery or unsettled weather around flowering, and if ever a season could be called unsettled,
2007 is surely the one," he says.

Nickerson cereal product manager Lee Robinson says that while _Fusarium_ was an issue for all wheats, it was of particular concern for quality wheat growers. "Whatever the variety, we would advise growers who have concerns about _Fusarium_ levels in their wheat this season to put it over a screen to remove small, shrivelled grains before submitting a sample to buyers," he says .

--
Communicated by:
J. Allan Dodds
Former ProMED-mail plant disease moderator <dodds@ucr.edu>

[Fusarium head blight (FHB; also known as scab) on wheat is caused by several fungal species originally classed into the genus _Fusarium_, accounting for the common name of this disease. Although some have since been re-assigned to different genera, the common name remains in use. Current names of the fungi mentioned above are _Gibberella zeae_ (previously _Fusarium graminearum_); _Fusarium poae_; _Monographella nivalis_ var. _nivalis_ (previously _Microdochium nivale_, synonym _Fusarium nivale_); and _Microdochium majus_.

FHB causes yield losses of up to 45 percent, reduces the grade of harvested grain, and it may also contaminate the grain with fungal toxins (mycotoxins; for example deoxynivalenol (DON), also known as vomitoxin which can affect stock). FHB is favoured by humid conditions during flowering and early stages of kernel development.
Symptoms are premature bleaching of infected spikelets and the production of orange, spore-bearing structures at the base of the glumes. During wet weather, there may be whitish, occasionally pinkish, fluffy fungal growth on infected heads in the field.
Diseased spikelets can contain visibly affected kernels. The grading term given to visibly affected wheat seeds is 'fusarium damaged kernels.'

FHB can also affect barley, oats, rye, maize and some grasses worldwide. Pathogens affecting these hosts may be different phylogenetic species or strains which are often limited to particular regions of the world. For more information on FHB on these hosts and on vomitoxin see ProMED-mail post number 20070621.2000.

The term 'lodging' refers to the collapse of cereal stems making grain harvest difficult. Lodging may be due to, for example, wind, rain pressure, or the extra weight of filled ears.

Map of the UK:
<http://www.lib.utexas.edu/maps/europe/united_kingdom.gif>

Pictures
Head blight symptoms, wheat:
<http://www.nwroc.umn.edu/Cropping_Issues/2005/issue6/FHB_examples.jpg>  and <http://plantsci.sdstate.edu/planthealth/other_images/scab.jpg>
FHB-damaged kernels of wheat, barley and oats:
<http://sci.agr.ca/charlottetown/images/wheatseedfhbt.jpg>
 
Links
Disease and toxin information:
<http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex92?opendocument>
_Fusarium_ head blight information:
<http://www.apsnet.org/education/feature/FHB/> and <http://smallgrains.psu.edu/pdf/FusariumHeadBlight.pdf>
_F. graminearum_ current species complex and FHB information:
<http://www.ars.usda.gov/Main/docs.htm?docid=9821>  and <http://www.cdl.umn.edu/pubs/pdfs/HCK/Pathogen_Profile.pdf>
Information on the mycotoxins via:
<http://cropwatch.unl.edu/>
_Gibberella zeae_ taxonomy:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=255496>
_Fusarium poae_ taxonomy:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=119380>
_Microdochium majus_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=345479>
_Monographella nivalis_ var. _nivalis_ taxonomy:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=445552>
Genus _Fusarium_ and _Microdochium_ list of species and synonyms via:
<http://www.indexfungorum.org/Names/Names.asp>
Home Grown Cereals Association UK:
<http://www.hgca.com/>
CropMonitor:
<http://www.cropmonitor.co.uk>
DEFRA website:
<http://www.defra.gov.uk/>
Nickerson Ltd. UK:
<http://www.nickersonuk.com/>
- Mod.DHA]

[see also in the archive:
Fungal blights, wheat, corn & chickpea - USA (NB, MT) 20070621.2000
2005
----
Fusarium head blight, wheat - USA (MN, ND) 20050812.2366 Wheat diseases, cereals - USA (ND) 20050731.2227 Wheat diseases - India 20050615.1683
2002
----
Fusarium head blight, oats - Canada (Manitoba) 20021017.5573
2001
----
Fusarium head blight, wheat - USA (Michigan) 20010725.1452 2000
----
Fusarium head blight: biological control 20000824.1416 Fusarium head blight, cereal - Canada (Manitoba) 20000823.1405 Fusarium head blight fungicide approved - Canada 20000624.1038
1999
----
Scab disease, wheat - Canada, USA 19990508.0756 Scab-resistant wheat, McVey cultivar - USA 19990801.1311]

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