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Date: 24 Mar 2008
Source: Resource Investor, Interfax-China report [edited]
<http://www.resourceinvestor.com/pebble.asp?relid=41387>

Outbreak of sharp eyespot disease in China threatens 4.83 million hectares of wheat

An outbreak of sharp eyespot disease (SED), which affects cereals, is threatening 72.46 million mu (4.83 million hectares) of wheat in China's major producing regions, according to local agricultural authorities.

SED might erode the wheat output by 10 to 20 percent, while a more serious epidemic could cut output by as much as 50 percent, officials from the Henan Oil and Grain Product Quality Inspection Center told Interfax. "As it is still the early growth stage for wheat, the impact on output might be reduced, although wheat quality may be downgraded," an official from the center said. Huang Junfei, a senior commodity analyst with Changjiang Futures, believes SED may well erode wheat output by around 5 percent on the 4.8 million affected hectares. As there are still a few months before the harvest, good farm work may be able to make up the losses.

The outbreak is being blamed on remnants of the disease from last year [2007], coupled with favourable conditions, including plentiful water supplies in some regions and weakened resistance caused by a cold snap earlier this year [2008]. Agricultural authorities caution that the peak season for SED normally lasts from mid and late March until mid April. SED outbreaks in major wheat producing regions by 10 Mar [2008] include [in decreasing order of affected area] Henan, Shandong, Jiangsu, Anhui, Hubei, and Shanxi provinces.

China's wheat cultivation in 2008 is expected to stay flat at around 23 million hectares with output expected to top 100 million tonnes.

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Communicated by:
ProMED-mail
<promed@promedmail.org>

[Sharp eyespot disease (SED) of wheat is caused by the soil-borne fungus _Ceratobasidium cereale_ (previously _Rhizoctonia cerealis_).
The pathogen can also affect barley, oats, rye, and some grass species and is prevalent throughout the temperate regions of the world. Symptoms are sharply defined lesions on the outer leaf sheaths and the stem. Lesions near the base of the stem have sharply defined dark margins and are lens shaped. Infected plants or tillers ripen and die prematurely producing white heads with shriveled kernels, and they often collapse. Infections are most serious when initiated on seedlings. Seedlings may be killed, or they may survive through the season and die before maturity. SED frequently occurs in combination with other fungal diseases.

The fungus can be spread with plant material and soil, as mycelium or as small resistant structures (sclerotia). While it is common, the damage is very dependent on the environment. SED is favoured by cool, wet conditions from late winter through early spring and often occurs around wet spots. Acidic soils increase disease risk. Rye and oats appear more susceptible than wheat or barley. SED can be severe on wheat when it follows more susceptible crops. Yield loss is related to disease incidence. It is considered negligible when the incidence is below 10 percent, but it can be considerable under conducive conditions. Losses are due to reductions in both grain numbers on ears and grain weight. Disease management relies mainly on cultural practices, including improvement of plant vigour, reduction of inoculum, good drainage, and crop rotation with non-host species.
Fungicide treatments are usually not considered reliable or cost effective.

There is little information on cultivar resistance, although some wheat varieties appear to differ in their susceptibility to SED. In China, variation in resistance between cultivars was reported to range from highly resistant to highly susceptible, but only 4-7 percent of all wheat lines tested, and as few as 1.7 percent of commercial cultivars were found to be resistant.

A disease with similar symptoms, known as eyespot or strawbreaker, is caused by an unrelated fungus in a different family (_Oculimacula yallundae_).

Maps
China:
<http://www.chinapage.com/map/map.html> and <http://healthmap.org/promed?v=36.5,103.9,4>
Provinces of China:
<http://www.sacu.org/provmap.html>

Pictures
SED symptoms on wheat leaves:
<http://scarab.msu.montana.edu/Disease/DiseaseGuidehtml/Img0079.jpg>
SED symptoms on wheat stems:
<http://www.hgca.com/hgca/wde/IMAGES/sharp.JPG>  and <http://scarab.msu.montana.edu/Disease/DiseaseGuidewebpics/Petewebpics51-60/Img0060.jpg>

Links
SED fact sheet:
<http://ohioline.osu.edu/ac-fact/0011.html>
SED information:
<http://www.hgca.com/hgca/wde/diseases/Sharp%20Eye/Sharhost.html>  and <http://www.omafra.gov.on.ca/english/crops/pub811/6eye.htm>
SED effects on wheat yield:
<http://www.rsnz.org/publish/nzjchs/2002/002.php>
Research on host resistance:
<http://www.nzpps.org/journal/58/nzpp58_268.pdf>
_C. cereale_ taxonomy and synonyms:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=107799>
List of wheat diseases and pathogens:
<http://www.apsnet.org/online/common/names/wheat.asp>.  - Mod.DHA]
 

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