ProMED
http://www.promedmail.org

Source: FreshPlaza [in German, trans. & summ. Mod.DHA, edited]
https://www.freshplaza.de/article/9690272/kakaopilz-bedroht-sudafrikas-papayaproduktion/

There are only a few papaya growers left now in South Africa. In 2019, a new disease emerged nationwide in papaya groves making trees fall to the ground. It was due to _Phytophthora palmivora_ (Pp) which is responsible for black pod of cocoa elsewhere. The pathogen was detected for the 1st time in South Africa in 2005 in a nursery on ornamental species.

Worldwide, papaya is the most common host of Pp, affecting the crop in areas of intensive cultivation, but the current study is the 1st time Pp was detected on papaya in South Africa. It is suspected that climate warming may have favoured the spread of the pathogen to that crop.

Pp was detected synchronously in regions more than 400 km [250 mi] apart. This may indicate that the disease could be connected with extreme weather conditions such as high temperatures and severe drought which dominated there in 2019. Pp has now spread to all papaya growing areas nationwide and is considered, at least in parts, to be responsible for the reduction in papaya cultivation nationally.

There is very little that can be done against Pp infection. In South Africa, no research is being funded on Pp of papaya since it is considered only a minor crop. Growers expect that there will be fewer and fewer fruit available, making them less and less affordable for consumers, if nothing is being done nationally about managing the problem.
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Communicated by:
ProMED

[Phytophthora root, crown and fruit rot on papaya is caused by the fungus-like organism _Phytophthora palmivora_. The pathogen attacks roots, stems and fruit and can completely destroy a crop. After infection, disease development is favoured by wet soil conditions. Symptoms include fruit rot and premature fruit drop, as well as root and stem rot leading to yellowing, wilting and collapse of leaves and eventual death of the plants. Roots are often completely destroyed and diseased trees emit a rotting smell. Plants can be infected at all ages but roots of young seedlings are most susceptible.

The pathogen is soil borne and can also be spread by plant material (including fruit), mechanical means, water and wind. Disease management may include cultural practices (soil drainage, crop rotation), phytosanitation (removal of pathogen reservoirs, quarantine measures) and use of clean planting material. Early fungicide treatments can reduce fruit rot and may make it possible to harvest some of the fruit from affected plantings, but will not save the mother plant.

_P. palmivora_ is known to affect more than 150 tropical hosts, including causing black pod of cocoa (e.g. ProMED post 20220913.8705557). New strains that spread faster and are more difficult to control are emerging.

Pictures
Papaya phytophthora rots:
https://c2.staticflickr.com/6/5030/5684242641_b0aedd1298_b.jpg,
https://live.staticflickr.com/2127/5794539067_687e8c4682_b.jpg,
https://live.staticflickr.com/5225/5681633506_facfae4d91_b.jpg,
https://www.business.qld.gov.au/__data/assets/image/0020/381080/varieties/thumbnail.png,
https://apps.lucidcentral.org/pppw_v10/images/entities/papaya_phytophthora_fruit__root_rot_152/paptree2.jpg,
https://apps.lucidcentral.org/pppw_v11/images/entities/papaya_phytophthora_fruit__root_rot_152/paptree3.jpg and
https://www.business.qld.gov.au/__data/assets/image/0028/381079/phytophthora-papaya-fig-1.jpg
Cocoa black pod:
https://apps.lucidcentral.org/pppw_v10/images/entities/cocoa_black_pod_006/dscn2677.jpg and
https://thecocoapost.com/wp-content/uploads/2019/07/20190528_095827.jpg
_P. palmivora_, micrograph:
https://agenciadenoticias.unal.edu.co/fileadmin/legacy/AgenciaNoticias_140915-01_11.jpg

Links
Information on phytophthora rots of papaya:
https://www.padil.gov.au/pests-and-diseases/Pest/Main/136594,
https://www.ctahr.hawaii.edu/oc/freepubs/pdf/pd-53.pdf,
https://www.horticulture.com.au/growers/help-your-business-grow/research-reports-publications-fact-sheets-and-more/pp23001/,
https://doi.org/10.1007/s10526-019-09948-y (biocontrol),
https://doi.org/10.1007/s40858-021-00464-y,
https://apps.lucidcentral.org/pppw_v10/text/web_full/entities/papaya_phytophthora_fruit__root_rot_152.htm and
https://www.business.qld.gov.au/industries/farms-fishing-forestry/agriculture/biosecurity/plants/diseases/horticultural/papaya-phytophthora-disease
Information on papaya rot and other _P. palmivora_ diseases (with pictures):
http://www.extento.hawaii.edu/kbase/crop/type/p_palmi.htm and
http://www2.ctahr.hawaii.edu/adap2/ascc_landgrant/Dr_Brooks/BrochureNo12.pdf
Information on cocoa black pod:
https://doi.org/10.1079/cabicompendium.40979,
https://apps.lucidcentral.org/pppw_v10/text/web_mini/entities/cocoa_black_pod_006.htm,
https://doi.org/10.1094/PHYTO-97-12-1650 and via
http://www.plantmanagementnetwork.org/pub/php/review/cacao/
Bud rot of palms:
https://edis.ifas.ufl.edu/publication/PP144,
https://doi.org/10.1094/PHYTO-09-15-0243-RVW (review) and
https://doi.org/10.1017/S0014479703001315 (review)
Information on other _P. palmivora_ diseases and hosts:
https://www2.ctahr.hawaii.edu/adap2/ascc_landgrant/Dr_Brooks/BrochureNo12.pdf
_P. palmivora_ taxonomy and synonyms (partly reclassified):
https://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=194605,
https://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=194605,
https://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=900853 and
https://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=900853
_Phytophthora_ diseases, impact and management:
http://www.baumkrankheiten.com/downloads/phytophthora-importance.pdf and via
https://edis.ifas.ufl.edu/publication/hs254
- Mod.DHA