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Date: 9 Jul 2007
Source: Australian Broadcasting Corporation Rural News [edited] <http://www.abc.net.au/rural/news/content/2007/s1973761.htm>

The discovery of a root disease on the western side of South Australia's Eyre Peninsula is threatening to cut crop yields by up to 50 percent. Rhizoctonia root rot is a root shrivelling disease, which occurs in low to medium rainfall areas where the soil is less fertile.

Agronomist Neil Cordon says because of cold weather the disease can be clearly seen in early sown crops. "Obviously if the season keeps going and if we get good rainfall you can get some compensatory growth from the plants surrounding the rhizoctonia bare patches and that can limit the yield loss, but some of the paddocks could [suffer] as high as 50 percent yield loss this year [2007]," he said.

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

******
[2] Date: Mon 9 Jul 2007
Source: Australian Broadcasting Corporation [edited] <http://www.abc.net.au/news/stories/2007/07/09/1973621.htm>

Farmers on South Australia's western Eyre Peninsula are facing a serious blow as they try to recover from the drought with a crop disease, which could wipe out up to half their yields. Rhizoctonia root rot, which causes roots to shrivel and reduces nutrient intake, is taking hold in a region from Streaky Bay to Elliston.

Neil Cordon from the Minnipa Agriculture Centre says it is a difficult problem to tackle. "Quite frankly we have not seen a silver bullet to control it ... it is soil borne, it's a fungus that survives in the soil ... over the years we've used some agronomic techniques to reduce the likelihood of getting rhizoctonia," he said.

"Farmers have tried all those techniques and it's not uncommon to come across farmers through the area that have tried this or do that as part of their agronomic package and still get hit."

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

[The affected crop is likely to be mainly wheat. Rhizoctonia root rot or bare patch is caused by _Rhizoctonia solani_ (current name _Thanatephorus cucumeris_) and is a severe disease of cereals in no-till cropping systems on many calcareous sandy soils of South Australia. It has a wide host range making it difficult to control by rotation, and it can also survive on roots of pasture grasses. The practice of herbicides replacing the plough to improve soil properties and prevent degradation has been widely adopted in Australia. However, the resulting build-up of organic matter favours the pathogen and it has become a serious problem associated with direct-drilled cropping practices.

Disease management practices may include seed treatment, fertiliser placement, timing of planting, resistant varieties, weed management during non-crop periods, and selection of the style of seed drill.

_T. cucumeris_ (_R. solani_) is a ubiquitous soilborne fungus, which causes damping-off, root rot, basal stem root (foot rot), and fruit rot in a large number of crops. It survives in soil, compost, and infected debris as mycelium. Many strains can infect wheat, one of which causes the bare patch syndrome.

Maps
Australia:
<http://www.ga.gov.au/image_cache/GA4073.jpg>
South Australia:
<http://www.ozhorizons.com.au/sa/map.htm>

Picture of _Rhizoctonia_ root symptoms:
<http://cbarc.aes.oregonstate.edu/cbarc/images/RRR-Pea-rootpruning.jpg>

Links
Disease description with pictures of bare patch:
<http://cbarc.aes.oregonstate.edu/cbarc/RhizoctoniaRootRot.htm>
Wheat root rot information:
<http://plantpathology.tamu.edu/Texlab/Grains/Wheat/wrrr.html>
<http://crops.confex.com/crops/2005am/techprogram/P5273.HTM>
History and background of wheat root rot in Australia:
<http://www.australasianplantpathologysociety.org.au/Pathology/McAlpine/DM7.htm>
_R. solani_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=229666>
Current name _T. cucumeris_ taxonomy:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=306777>. - Mod.DHA]

[see also in the archive:
2004
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Regulated plant pests, detection, March 2004: EPPO 20040710.1850
2002
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Rhizoctonia oryzae, pea, first report - N. America 20020516.4225]

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