Sunday, 21 April 2024 08:16:00
Grahame Jackson posted a new submission ‘STUNT DISEASE, MAIZE – ARGENTINA’
Submission
STUNT DISEASE, MAIZE – ARGENTINA
ProMED
http://www.promedmail.org
Source: Reuters [summ. Mod.DHA, edited]
https://www.reuters.com/markets/commodities/argentina-corn-harvest-faces-more-deep-cuts-stunt-disease-spread-2024-04-17/
Argentina’s maize harvest faces deep cuts due to a stunt disease spread by leafhoppers. The crop has been hit by an unprecedented outbreak of the insects that carry the harmful spiroplasma. Leafhopper populations tend to increase in hot and dry conditions. They have badly dented the 2023/24 maize crop, which is very badly affected.
In the worst-hit northern provinces the losses caused by the disease range between 40% and 50%, when normally the figure reached only 5% at worst. Severe cases of leafhoppers were also being seen in regions where they usually do not appear. The unusually damaging outbreak this year has reached areas where it never reached before.
In response, the government announced it was accelerating approval procedures for 2 insecticides recommended to combat the spiroplasma disease, although that comes largely too late for the current harvest. Another factor that will determine how the outbreak progresses is the arrival of low temperatures, as the insect cannot resist temperatures below 4 degrees Celsius. However, scientists at the University of Buenos Aires said that a rapid decrease in temperatures was not expected in northern Argentina, the location of the worst outbreaks.
[Byline: Maximilian Heath]
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Communicated by:
ProMED
[_Spiroplasma kunkelii_ causes maize stunt disease on _Zea_ species in the Americas. The maize leafhopper _Dalbulus maidis_ is the main vector. Some crop hybrids resistant to the vector have been identified which potentially may be helpful in disease control (see links below).
Spiroplasmas are plant cell parasitic bacteria without a cell wall and, like phytoplasmas, belong to the mollicutes. The name is derived from their helical morphology. Spiroplasmas can be cultured on artificial media, unlike phytoplasmas, which cannot be cultured in vitro. Mixed infections with phytoplasmas have been reported to occur.
The pathogens are transmitted by leafhopper species. Disease management for spiroplasmas mainly relies on exclusion by use of certified clean planting material, but may also include phytosanitation to remove inoculum and prevent spread within plantings. Vector control has not shown to be effective due to the very rapid transmission.
The related _S. citri_ causes citrus stubborn disease (CSD, also called little leaf); yield losses may be severe (ProMED post 20200710.7559217). The pathogen is also known to affect other crops causing, for example, carrot purple leaf (ProMED post 20110916.2824) and horseradish brittle root diseases.
Pictures
Maize stunt symptoms:
https://bugwoodcloud.org/images/768×512/1235015.jpg,
https://live.staticflickr.com/4095/4927676830_083918e066_b.jpg,
https://bugwoodcloud.org/images/768×512/1524072.jpg
https://agribrasilis.com/wp-content/uploads/2023/02/Hibrido-suscetivel-777×437.jpg (ears) and
https://www.researchgate.net/profile/Pablo-Carpane/publication/280309801/figure/fig1/AS:934279647354880@1599761034390/Figura-1-Corn-stunt-spiroplasma-en-maiz.png
Citrus stubborn disease symptoms:
https://www.dpi.nsw.gov.au/__data/assets/image/0004/597370/reduced-size-fruit.jpg,
https://www.plantmanagementnetwork.org/pub/php/symposium/melhus/8/stubborn/image/stubborn4sm.jpg and
https://content.peat-cloud.com/w600/citrus-stubborn-disease-citrus-1.jpg
_S. citri_ microscopy:
https://iant.toulouse.inra.fr//bacteria/annotation/web/img/spiroplasma.jpg
Links
Information on maize stunt disease:
https://doi.org/10.3390/plants9060747,
https://doi.org/10.1371/journal.pone.0234454,
https://doi.org/10.1371/journal.pone.0259481,
https://agribrasilis.com/2023/02/27/corn-stunt2/,
https://www.gardeningknowhow.com/edible/vegetables/corn/treating-stunt-disease-in-corn.htm,
https://link.springer.com/article/10.1007/s40858-023-00598-1 and via
https://www.ars.usda.gov/northeast-area/beltsville-md-barc/beltsville-agricultural-research-center/molecular-plant-pathology-laboratory/docs/spiroplasma-kunkelli-genome-sequencing-project/corn-stunt-disease/
Citrus stubborn disease:
https://doi.org/10.1079/cabicompendium.50977,
https://www.planthealthaustralia.com.au/wp-content/uploads/2015/01/Citrus-stubborn-disease-FS.pdf,
https://plantix.net/en/library/plant-diseases/300017/citrus-stubborn-disease and
http://www.plantmanagementnetwork.org/pub/php/symposium/melhus/8/stubborn/
Spiroplasma taxonomy via:
https://www.uniprot.org/taxonomy/2132
Information on leafhopper vectors via:
https://bugguide.net/node/view/63
– Mod.DHA
Global Plant Protection News 