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: Sat 12 Apr 2015
Source: Imagen del Golfo [in Spanish, machine transl., summ. Mod.DHA, edited] <http://www.imagendelgolfo.com.mx/resumen.php?id=41060361>
Maize crops are being lost due to an outbreak of tar spot in parts of the south-eastern zone of Veracruz. In addition, sorghum crops are affected by several types of aphids.
Farmers in the region are asking for government support whenever 50 per cent of their maize crops or 25 per cent of their sorghum crops are lost.
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Communicated by: ProMED-mail <promed@promedmail.org>
[Tar spot of maize is a disease complex, which has been known to cause serious yield losses of up to 75 per cent in Central and South America. It is caused by the association of at least 3 fungal species:
_Phyllachora maydis_, _Monographella maydis_ and _Coniothyrium phyllachorae_.
Of these, _P. maydis_ is usually the first to cause leaf lesions.
While _M. maydis_ is a common benign saprophyte on leaf surfaces, it becomes highly virulent only in association with _P. maydis_ and forms necrotic rings around the _P. maydis_ lesions. _C. phyllachorae_ may be a hyperparasite of the other 2, but its role is not fully understood yet. Leaf lesions may coalesce causing blight and complete burning of the foliage. In addition, characteristic black, shiny spots ("tar spots") are produced both within lesions and on other leaf areas. Affected ears have fewer kernels which may germinate prematurely on the cob.
_P. maydis_ is an obligate parasite, its spores are spread by wind, and it produces a potent toxin killing plant tissue. The disease is favoured by cool, humid conditions. Disease management relies mainly on the use of resistant maize varieties, however little is known about the genetics of tar spot resistance.
Maps
Mexico:
<http://www.lib.utexas.edu/maps/americas/mexico_pol97.jpg>
Veracruz:
<http://www.explorandomexico.com/photos/maps/full-veracruz_l.gif>
Pictures
Tar spot symptoms on maize via:
<http://www.flickr.com/photos/cimmyt/sets/72157624712558456/detail/>
Links
Information on tar spot complex of maize:
<http://cat.inist.fr/?aModele=afficheN&cpsidt=3692273>,
<http://www.springerlink.com/content/g0wq78p421737137/>,
<http://cat.inist.fr/?aModele=afficheN&cpsidt=3371810>,
<http://cat.inist.fr/?aModele=afficheN&cpsidt=5320652> and <http://www.informaworld.com/smpp/content~content=a905495708~db=all~order=page>
_Phyllachora maydis_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=167673>
_Monographella maydis_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=104487>
_Coniothyrium phyllachorae_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=178431>
- Mod.DHA]
[See Also:
2013
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Tar spot, maize - El Salvador: 1st rep (LI) 20130411.1639445
2011
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Tar spot, maize - Honduras: spread 20110210.0456
2009
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Undiagnosed fungus, maize - Guatemala (02): tar spot 20090420.1491 Undiagnosed fungus, maize - Guatemala: RFI 20090220.0710]
Topics
Species
