A ProMED-mail post
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International Society for Infectious Diseases
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Date: Fri 10 Jan 2025
Source: Proplanta [in German, trans. & summ. Mod.DHA, edited]
https://www.proplanta.de/agrar-nachrichten/pflanze/runder-tisch-zur-schilf-glasfluegelzikade-die-lage-ist-ernst_article1736532731.html


The situation with regard to the plant hopper spreading 2 diseases of sugar beet is considered serious, and discussions are being held. SBR and the stolbur pathogen [see comments below] are the biggest challenge for agriculture in the coming years. It is reassuring that the extent of the problem has been acknowledged clearly by the Federal Ministry for Food and Agriculture, ensuring official support in the development of solutions by the beet industry. Without that support, national food production would be under serious threat.

The plant hopper vector has been spreading extensively during the last years. The SBR/stolbur diseases are leading to severe reductions of yield and produce quality. In 2023, 40 000 ha were affected; in 2024 it was already at least 75 000 ha. This amounts to approximately 20% of area cultivated with beets. Severely affected regions are found mainly in Baden-Wuerttemberg [ProMED post 20231023.8712769], Bavaria, and Rhineland-Palatinate. Incidence is in no way restricted to individual agricultural units, but whole ecological regions are affected. Without control measures, a further increase is to be expected.

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Communicated by:
ProMED

[The same plant hopper species, _Pentastiridius leporinus_, was found to be the vector of phloem-restricted prokaryotes associated with 2 sugar beet diseases: syndrome des basses richesses (SBR) and rubbery taproot. The pathogens cannot be cultivated. Further information is needed to clarify the role of each of the pathogens and any potential interactions in causing disease.

[1] Syndrome des Basses Richesses (SBR) was first described on sugar beet crops in the Burgundy and Franche-Comte regions of France. Both a γ-proteobacterium, _Candidatus_ Arsenophonus phytopathogenicus, and a stolbur phytoplasma were found to be associated with the disease. Symptoms on sugar beet include yellowing and curling of older leaves leading to new growth of central leaves which show chlorosis and distortion. Roots are of normal size, but vascular bundles are brown. Sugar content of the beets suddenly decreases before harvest in autumn. Yield losses resulting in up to 50 percent loss of income from the crop ("basses richesses") have been reported. In Germany, potato has recently been identified for the first time globally as a new host of this pathogen (ProMED post 20231009.8712531).

[2] _Candidatus_ Phytoplasma solani is the type member of the stolbur (16SrXII) phytoplasma taxonomic group. A stolbur strain has been identified as the cause of sugar beet rubbery taproot disease in Serbia (ProMED post 20201012.7856600). Stolbur phytoplasmas, alone or in coinfections, have been reported to affect a range of dicotyledoneous crops (including tomato, potato, capsicum, aubergine, grapevine, sugar beet), as well as a few monocot hosts such as maize and sugar cane (ProMED posts 20070607.1844, 20080303.0869).

Disease management for both pathogens may include vector control, removal of pathogen and/or vector reservoirs (volunteer crop plants, weeds), use of clean planting material, and phytosanitary measures for prevention of spread to new areas.

A northward spread of the vector due to climate warming is being recorded in Europe. Other recent examples of such events from the region are some bacterial and fungal species (e.g., ProMED posts 20241008.8719235,20130927.1970792, 20090914.3230, 20110718.2172). The phytosanitary risk for SBR/stolbur for Europe has been declared as high; crop monitoring has been recommended for areas under threat which needs to include all known host crops.

Pictures
Symptoms of sugar beet stolbur rubbery taproot disease:
https://apsjournals.apsnet.org/cms/10.1094/PDIS-07-20-1602-RE/asset/images/medium/pdis-07-20-1602-ref1.gif,
https://stmaaprodfwsite.blob.core.windows.net/assets/sites/1/2024/04/Early-symptoms-RTD-_C_Zivko-Curcic-1024x577.jpg (affected field) and
https://spudsmart.com/wp-content/uploads/2023/01/IMG_1264-1536x2048.jpg (in potatoes)
SBR symptoms on sugar beet:
https://bisz.suedzucker.de/wp-content/uploads/2018/10/Schadbild3-1024x595.png (affected field),
https://bisz.suedzucker.de/wp-content/uploads/2018/10/Schadbild2-1024x589.png (tuber, healthy on left) and
https://bisz.suedzucker.de/wp-content/uploads/2018/10/Schadbild1-1024x645.png (crown, healthy on left)
Rubbery taproot & SBR vector insects:
https://bisz.suedzucker.de/wp-content/uploads/2018/10/Zikade1.jpg

Links
Information on sugar beet stolbur rubbery taproot disease:
https://doi.org/10.1094/PDIS-07-20-1602-RE,
https://www.fwi.co.uk/arable/sugar-beet/sugar-beet-rubbery-taproot-disease-what-farmers-need-to-know and
https://spudsmart.com/a-new-disease-called-rubbery-rot-is-lurking-in-potato-storages/ (in potato, North America)
Information on SBR and associated pathogens:
https://gd.eppo.int/download/doc/985_minids_ARSEPH.pdf,
https://doi.org/10.1094/PHYTO-97-0072,
https://doi.org/10.1094/PHYTO.2002.92.4.384
https://doi.org/10.1007/s10658-006-9087-3 and
https://doi.org/10.3390/insects14030281 (new host potato)
SBR/stolbur in Europe (in German):
https://www.proplanta.de/agrar-nachrichten/pflanze/zu-niedrige-zuckergehalte-ruebenbauern-unter-druck_article1733191828.html (low sugar content),
https://www.proplanta.de/agrar-nachrichten/pflanze/schaetzung-der-zuckerproduktion-deutlich-gesenkt_article1731922704.html (nationwide yield reduction) and
https://www.proplanta.de/agrar-nachrichten/pflanze/ruebenanbauer-draengen-auf-hilfe-wegen-schilf-grasfluegelzikade_article1731243407.html (northward spread of vector)
Vector interactions:
https://doi.org/10.1111/eea.12766,
https://doi.org/10.1007/s10658-009-9520-5,
https://doi.org/10.1016/j.jip.2007.09.009 and
https://doi.org/10.1094/PDIS-92-1-0113
Phytoplasma & Arsenophonus taxonomy and species lists via:
https://www.uniprot.org/taxonomy/33926
Information on _P. leporinus_ vector:
https://gd.eppo.int/taxon/PNSTLE
Information on phytoplasma vectors (with pictures) via:
http://www.psyllids.org/index.htm
- Mod.DHA]

See Also

2024
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Rubbery taproot & basses richesses, sugar beet - Germany 20241210.8720556
2023
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Stolbur rubbery taproot, sugar beet - Germany: (BW) 20231023.8712769
Basses richesses, potato - Germany: new global host record 20231009.8712531
2020
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Rubbery taproot disease, sugar beet - Serbia: cause 20201012.7856600
2012
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Basses richesses, sugar beet - Germany: 1st rep. 20121205.1439837
2002
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Phytoplasma, new, sugarbeet - France 20020324.3812
and additional items on stolbur diseases in the archive

Website: http://www.isid.org

Published: January 20, 2025