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Downey mildew on maize in Tamil Nadu, India

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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: 7 November 2008
Source: Business Standard [edited]
<http://www.business-standard.com/india/storypage.php?autono=339418>

Mildew hits maize in TN

Maize production in Tamil Nadu (TN), which accounts for 83 per cent of the country's maize production, has been hit by the downy mildew disease, according to Tamil Nadu Agricultural University.

India has the world's 5th largest maize acreage with over 7 million hectares (17.3 million acres) and it is the 3rd most important cereal. This year [2008], maize production has been hit in Coimbatore, Udumalapet, Darapuram, Odanchatram, Dindigul, and Theni, the major districts that cultivate maize, due to the infestation of downy mildew disease.

The downy mildew group of fungi is seedborne. It affects plant development as infestation is at the early stage (30 days) of crop development. The disease could intensify when the relative humidity is high and could be a major constraint in maize production, according to university's release.

Maize has gained in popularity with farmers in Tamil Nadu as a more remunerative crop and simple management practices, and farmers have begun to cultivate 2-3 crops in a year. Continuous cropping and congenial environment has led to development of pests.

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[Downy mildews are important maize pathogens in many tropical regions of the world. They are particularly destructive in Asia, where losses in excess of 70 per cent have been documented. Around 10 different species of downy mildew fungi in the genera _Peronosclerospora_, _Sclerospora_, and _Sclerophthora_ have been reported to affect maize. In India, a number of these pathogens occur, but _P. sorghi_ (sorghum downy mildew) and _Sclerophthora rayssiae_ (brown stripe downy mildew) are considered common.

Symptoms of the different downy mildew species on maize are similar, although they can vary with plant age, climatic conditions, and host germplasm. Infection at the seedling stage results in stunting, chlorosis, and premature plant death. Infection of older plants results in leaf symptoms of mottling, chlorotic streaking, lesions, and may produce white striped leaves that eventually shred. 'Downy' growth often occurs on leaves and is more common on the lower leaf surface. Plants may be stunted, tiller excessively, have malformed tassels and ears, and may not produce seed.

Downy mildew spores are spread within a crop mainly by splashing rain, wind, or mechanical means. The fungi survive between crops on infected plant material or alternate weed hosts. Some of the maize pathogens can also be seedborne, although this is largely restricted to seed that is fresh and has a high moisture content. Downy mildews are usually controlled with fungicides.

Maps
India:
<http://www.globalsecurity.org/military/world/india/images/IndiaMap_tourism.gif
and
<http://healthmap.org/promed?v=22.9,79.6,5>
Tamil Nadu districts:
<http://www.mapsofindia.com/maps/tamilnadu/tamilnadu-district.htm>
Karnataka districts:
<http://www.mapsofindia.com/maps/karnataka/karnataka.htm>
Pictures
Maize with downy mildews:
<http://www.cimmyt.org/Research/maize/maizepathologyresearch/Images/path1.jpg
and
<http://cril.cimmyt.org/gallery/main.php?g2_view=keyalbum.KeywordAlbum&g2_keyword=maize&g2_itemId=365

Information on maize downy mildews:
<http://maizedoctor.cimmyt.org/index.php?id=233&option=com_content&task=view>,
<http://www.ikisan.com/links/ap_maizeDisease%20Management.shtml>,
<http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.py.15.090177.001341>, 
and
<http://cril.cimmyt.org/gallery/main.php?g2_view=keyalbum.KeywordAlbum&g2_keyword=maize&g2_itemId=153

 

 

 

 

 

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