Grahame Jackson/ PestNet
Sydney NSW, Australia
For your information
6 days ago
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TAR SPOT, MAIZE – ECUADOR
ProMED
http://www.promedmail.org
Source: Reliefweb, FAO report [summ. Mod.DHA, edited]
https://reliefweb.int/report/ecuador/giews-country-brief-ecuador-15-june-2022
In Ecuador, harvesting of the 2022 main season maize crops is ongoing under favourable weather conditions. Yields are expected to be below average due to low precipitation in key producing provinces. In addition, a fungal disease called tar spot (mancha de asfalto) reportedly affected maize crops, with negative effects on yields.
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Communicated by:
ProMED
[Tar spot of maize has been known to lead to serious yield losses of up to 75% in Central and South America. It is considered to be a disease complex involving the synergistic association of at least 3 fungal species: _Phyllachora maydis_, _Microdochium maydis_ (previously _Monographella maydis_) and _Coniothyrium phyllachorae_.
Of these, _P. maydis_ is usually the 1st 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. Weakening of stems may lead to increased lodging. The disease reduces photosynthetic potential and therefore plant vigour.
_P. maydis_ is an obligate parasite; its spores are spread by wind and with infected plant material. It produces a potent toxin killing plant tissue. The disease is favoured by cool, humid conditions. Tar spot management may include fungicide treatments and use of maize varieties with tolerance or low sensitivity to the disease. However, resistance breeding is difficult because of the involvement of multiple pathogens. So far, little is known about the genetics of tar spot resistance.
Maps
Ecuador:
https://www.worldometers.info/img/maps/ecuador_physical_map.gif and
https://images.mapsofworld.com/ecuador/ecuador-political-map.jpg (provinces)
Americas, overview:
https://www.worldofmaps.net/typo3temp/images/karte-nord-und-suedamerika.jpg
Pictures
Tar spot on maize leaves:
https://ipcm.wisc.edu/wp-content/uploads/sites/54/2018/12/IMG_0418.jpg and
https://ag.purdue.edu/btny/cdcruzlab/wp-content/uploads/2020/04/TS16-scaled.jpg
Tar spot symptoms on maize ears:
https://www.canr.msu.edu/corn/uploads/images/Tar%20spot%20on%20ear%20-%20cropped.jpg,
http://i.ytimg.com/vi/ErB9pdiXPp4/maxresdefault.jpg and
https://c1.staticflickr.com/5/4123/4886728754_57fe0982e9_b.jpg
Links
Information on tar spot complex of maize:
https://doi.org/10.1094/PDIS-02-20-0449-FE,
https://www.extension.purdue.edu/extmedia/BP/BP-90-W.pdf,
https://www.agweb.com/news/crops/crop-production/tar-spot-what-you-need-know-about-new-corn-disease,
https://www.researchgate.net/publication/266732736_Tar_Spot_Complex_of_Maize_Facts_and_Actions,
https://doi.org/10.1111/j.1365-3059.1995.tb01671.x,
https://www.youtube.com/watch?v=ErB9pdiXPp4 and
https://www.apsnet.org/publications/phytopathology/backissues/Documents/1992Articles/Phyto82n05_505.PDF
Tar spot information & resources via:
https://www.cimmyt.org/tag/tar-spot-complex/
Recent updates on tar spot in North America:
https://phys.org/news/2022-01-pathologists-collaborate-knowledge-threat-corn.html,
https://www.newfoodmagazine.com/news/161116/plant-pathologists-leading-fight-against-damaging-corn-disease-tar-spot/ and
https://eu.thedailyreporter.com/story/news/2022/02/22/msue-farmer-education-day-focuses-corn-tar-spot-which-hit-michigan/6881223001/
_Phyllachora maydis_ taxonomy:
http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=167673
_Microdochium maydis_ taxonomy and synonyms:
http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=811970 and
http://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=811970
_Coniothyrium phyllachorae_ taxonomy:
http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=178431
– Mod.DHA
Maize
Tar_spot
Global Plant Protection News 
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