• Widespread. In Oceania only from Wallis and Futuna. Mostly, confined to cassava; some weeds are hosts.
• Diseases cause yellowing of leaves, bunching of shoots - growth of normally dormant buds - sometimes vascular tissue discolouration, occasionally leaf mosaics, rough skin, cracking, woodiness of storage roots. Yield and starch losses impact farmers and processors. Examples include:
  • Cassava frogskin (South America). Symptoms mainly on storage roots: thin, woody, deep cracks, sometimes forming rings around roots.
  • X-disease (Brazil). Yellow, distorted leaves; stunting; witches’ broom symptoms.
  • Witches’ broom (Thailand, Vietnam). Symptoms of witches’ broom; browning of vascular tissues; poor storage root development.
  • Unnamed (Uganda). Yellowish leaves; slight stunting.
  • Unnamed (Cote d’Ivoire). Yellowing of leaves and mosaic patterns. Similar phytoplasma to St Paul Wilt Disease of coconut.
  • Unnamed (Wallis and Futuna). Yellowing and bunching of shoots.
• Spread: cuttings for propagation; possibly, phloem-feeding insects (leafhoppers and planthoppers).
• Biosecurity: risk from unofficial introduction of diseased cuttings for propagation. Official movement of germplasm should follow the FAO/IPBGR Technical Guidelines.
• Biocontrol: none.
• Cultural control: take cuttings from apparently healthy plants; rogue plants with symptoms; avoid planting next to cassava with disease.
• Chemical control: not a method to use, as little known about spread by insects.

Cassava phytoplasma diseases.

Classified as Candidatus Phytoplasma, with the species determined by tests of the 16S ribosomal RNA gene. The phytoplasmas of cassava fall into several groups, e.g., Candidatus Phytoplasma asteris, 16SrI;  Candidatus Phytoplasma aurantifolia, 16SrII, and others. This way of naming them will remain until they can be cultured and tests prove they are the cause of the diseases associated with them.