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Source: FreshPlaza, Citrus Industry report [summ. Mod.DHA, edited]

The 1st cases of plants with citrus greening disease have been confirmed in Uruguay, according to a health emergency note released by the country's Ministry of Livestock, Agriculture and Fisheries. Plants with symptoms were found in a residence in Artigas Department.

After laboratory analysis, the presence of the disease was confirmed. Inspections were carried out in the surroundings of the outbreak and no new positive cases were detected. Measures were adopted to prevent the spread of the disease, including constant monitoring of homes and farms following an action plan developed earlier for the management and control of citrus greening.

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[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 (e.g. ProMED posts 20180214.5629251, 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 (e.g. ProMED posts 20181119.6154764, 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 (e.g. ProMED posts 20160902.4459660, 20160622.4302098, 20160509.4211696) migrating to new areas in many regions due to warming climates.

In the report above, it is not specified which of the 3 liberibacters has been identified in Uruguay. While CaLas appears to be the likely pathogen, both the Asian and South American species are present in neighbouring Brazil and other parts of the region.

Uruguay (with departments): and,2369
South America, overview:

Citrus greening symptoms:,, and
Asian greening, symptoms and vector photo galleries:

Citrus greening information: and
Asian greening, information & distribution:, and
African greening, information & distribution: and
American greening, information & distribution:
Taxonomy of Liberibacter species via:
Taxonomy and information for psyllid vectors (with pictures) via:
- Mod.DHA]


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