A
ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
Date: 15 Jun 2009
Source: Stock & Land [edited]
<http://sl.farmonline.com.au/news/state/grains-and-cropping/general/rhizoctonia-alert-for-vic-growers/1540859.aspx>
Rhizoctonia alert for growers
Rhizoctonia bare patch could be the main soil borne disease risk
to cereal crops -- particularly those sown late -- this season
according to the Grains Research and Development Corporation
(GRDC).
GRDC manager for crop protection Dr Rohan Rainbow said recent
dry seasons and reduced carbon inputs from crop residues had
caused a decline in general biological activity, and this had
favoured high levels of rhizoctonia fungus. "Data from testing
of soil samples from
415 paddocks across southern Australia showed that levels of
rhizoctonia were generally high in most cropping regions in
South Australia, as well as in western Victoria, the Geraldton
and Esperance regions of Western Australia and Deniliquin in New
South Wales," Dr Rainbow said.
"Sowing the crop early while the soil is still warm, and
encouraging early seedling vigour, is the best short-term
strategy. Other measures growers can take to reduce the impact
of the disease include deep banding nitrogen, minimising stubble
incorporation at seeding, ensuring adequate nutrition, and
controlling autumn growth early."
--
Communicated by:
ProMED-mail
<promed@promedmail.org>
[Rhizoctonia root rot (or bare patch) of cereals is caused by
_Thanatephorus cucumeris_ (previously _Rhizoctonia solani_), a
ubiquitous soil borne fungus associated with damping-off, root
rot, basal stem rot (foot rot), and fruit rot in a large number
of crops.
It causes crop damage by pruning the root system, which results
in water and nutrient stress to the plant. Yield losses of up to
50 percent have been reported in cereal crops. The pathogen
survives in the upper soil, compost, and infected plant debris,
and inoculum levels increase on the roots of host plants.
The fungus has a wide host range, including cereals, pasture
grasses, oilseed rape, and pulses, making it difficult to
control by crop rotation. Disease management may include seed
treatments, cultural practices (such as fertiliser applications,
timing of planting, weed management during non-crop periods,
selection of the style of seed drill), and use of resistant crop
varieties.
The practice of herbicides replacing the plough to improve soil
properties and prevent land degradation has been widely adopted
in Australia. However, the resulting build-up of organic matter
and preservation of fungal structures in the soil favours the
pathogen and consequently these direct-drilled cropping systems
often face very serious rhizoctonia problems.
High levels of inoculum in the soil increase the risk of crop
damage.
Other factors, especially soil suppressive activity, which is a
function of the population, activity, and composition of the
soil microbial community, also play a role in disease
development. Both high soil inoculum and reduced soil
suppressive activity is being reported above compounding the
risk for the indicated areas.
Maps of Australia:
<http://www.ga.gov.au/image_cache/GA4073.jpg>
and <http://healthmap.org/r/00cS>
Pictures
Rhizoctonia bare patch in wheat:
<http://www.agric.wa.gov.au/objtwr/imported_images/rhizocto_webpic.jpg>
Root pruning symptoms in pea:
<http://cbarc.aes.oregonstate.edu/cbarc/images/RRR-Pea-rootpruning.jpg>
Links
Rhizoctonia fact sheet (with pictures):
<http://www.grdc.com.au/uploads/documents/GRDC_FS_rhizo.pdf>
Rhizoctonia root rot information:
<http://cbarc.aes.oregonstate.edu/cbarc/RhizoctoniaRootRot.htm>
and <http://crops.confex.com/crops/2005am/techprogram/P5273.HTM>
_T. cucumeris_ taxonomy and synonyms:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=306777>
GRDC:
<http://www.grdc.com.au/>.
- Mod.DHA]
[see also
in the
archive:
2007
----
Rhizoctonia root rot - Australia (SA) 20070717.2291
2004
----
Regulated plant pests, detection, March 2004: EPPO
20040710.1850] |
|
