ProMED
http://www.promedmail.org

Source: FreshPlaza, Citrus Industry report [summ. Mod.DHA, edited]
https://www.freshplaza.com/europe/article/9463861/hlb-and-canker-incidences-are-increasing-in-brazil/

The average incidence of greening disease in Brazil's citrus belt has increased from 22% in 2021 to 24% in 2022. In some regions, where the incidence was already high in previous years, greening increased to over 74%.

The disease is increasing at a worrying speed overall and more control efforts are needed. Some areas that have taken measures to combat greening have registered a decline or stabilisation of disease incidence, suggesting that the measures can be effective.
--
Communicated by:
ProMED

[Citrus greening (CG) is one of the most damaging diseases of the crops, affecting leaves and fruit. It is caused by fastidious phloem-inhabiting bacteria classified as _Candidatus_ Liberibacter asiaticus (CaLas; Asian greening; huanglongbing), africanus (including a subsp. capensis; African greening), or americanus (South American greening). The 3 pathogens can only be distinguished by molecular methods. Several phytoplasma species have been reported to cause symptoms similar to greening disease in citrus; coinfections of phytoplasmas with CaLas have also been recorded (see, for example, ProMED posts 20180214.5629251 and 20190329.6392077). Further research is needed on symptomatology, epidemiology, and host impact of both single and mixed infections of these pathogens.

Symptoms may include blotchy mottling and yellowing of leaves, as well as small, irregularly shaped fruits with a thick, pale peel and bad taste. Early symptoms may be confused with nutrient deficiencies. Affected trees become stunted, bear multiple off-season flowers, and may live for only a few years without ever bearing usable fruit. CG is restricted to _Citrus_ and close relatives because of the narrow host range of its psyllid vectors. The pathogens can also be spread by grafting and possibly by seed from infected plants or transovarially in the vector insects. Both pathogens and vectors can be spread with plant material.

Disease management requires an integrated approach including use of clean planting and grafting stock, elimination of inoculum, use of pesticides for vector control in orchards, as well as chemical or biological control of vectors in non-crop reservoirs. Control using cultural methods, such as interplanting with non-host crops, is being trialled. In areas where a pathogen has not yet been detected, biological control of vectors has been used successfully to reduce insect numbers and, therefore, the risk of greening outbreaks (see, for example, ProMED post 20090601.2034).

Antibiotics as leaf sprays, seed treatments, or trunk injections are being used occasionally to treat CG (see, for example, ProMED posts 20181119.6154764 and 20190320.6377319), but are subject to strict regulations in most countries due to their associated risks of facilitating the emergence of antibiotic resistances in other crop, animal, and human pathogens. Furthermore, beneficial soil microbes may be killed off as collateral damage, making the plants weaker and more susceptible to other diseases. Residues of antibiotics may also lead to rejection of exported produce by some countries.

In South America, citrus in colder areas has been found less affected by CG (ProMED post 20201207.7999673), possibly due to vector insects in colder temperatures being less active. However, elsewhere citrus psyllids have been found at increasing altitudes (ProMED post 20161129.4660906), potentially due to increasing overall temperatures there. This reflects similar effects observed for other pathogens and pests (see, for example, ProMED posts 20160902.4459660, 20160622.4302098, and 20160509.4211696) migrating to new areas in many regions due to warming climates.

Maps
Brazil:
https://www.worldatlas.com/webimage/countrys/samerica/lgcolor/brnewzzl.gif and
https://promedmail.org/promed-post?place=8705985,6
South America, overview:
http://ontheworldmap.com/south-america/political-map-of-south-america.jpg

Pictures
Citrus greening symptoms:
http://www.citrusalert.com/wp-content/uploads/2012/10/GreenIslandsOfColor.jpg,
https://geneticliteracyproject.org/wp-content/uploads/2016/10/citrus_greening.jpg, and
http://www.abc.net.au/reslib/200904/r362894_1677317.jpg
Citrus greening, symptoms and vector photo galleries:
http://www.invasive.org/browse/subinfo.cfm?sub=4695 (Asian) and
https://gd.eppo.int/taxon/LIBEAF/photos (African)

Links
Citrus greening information:
http://cisr.ucr.edu/citrus_greening.html and
https://www.aphis.usda.gov/aphis/resources/pests-diseases/hungry-pests/the-threat/citrus-greening/citrus-greening-hp
Asian greening, information and distribution:
http://www.cabi.org/isc/datasheet/16565 and
http://www.planthealthaustralia.com.au/pests/huanglongbing-or-citrus-greening-asiatic-strain/
African greening, information and distribution:
http://www.cabi.org/isc/datasheet/16564
Taxonomy of Liberibacter species via:
http://www.uniprot.org/taxonomy/34019
Taxonomy and information for psyllid vectors (with pictures) via:
http://www.psyllids.org/index.htm
- Mod.DHA]