Lethal yellowing (LY) is a

phytoplasma Phytoplasmas are obligate intracellular parasites of plant phloem tissue and of the insect vectors that are involved in their plant-to-plant transmission. Phytoplasmas were discovered in 1967 by Japanese scientists who termed them mycoplasma-lik ...

disease that attacks many species of palms, including some commercially important species such as the

coconut The coconut tree (''Cocos nucifera'') is a member of the palm tree family ( Arecaceae) and the only living species of the genus ''Cocos''. The term "coconut" (or the archaic "cocoanut") can refer to the whole coconut palm, the seed, or the ...

and

date palm ''Phoenix dactylifera'', commonly known as date or date palm, is a flowering plant species in the palm family, Arecaceae, cultivated for its edible sweet fruit called dates. The species is widely cultivated across northern Africa, the Middle Eas ...

. In the Caribbean it is spread by the

planthopper A planthopper is any insect in the infraorder Fulgoromorpha, in the suborder Auchenorrhyncha, a group exceeding 12,500 described species worldwide. The name comes from their remarkable resemblance to leaves and other plants of their environment ...

Haplaxius crudus ''Haplaxius crudus'' is a planthopper species in the genus '' Haplaxius''. ''H. crudus'' is the vector of the coconut lethal yellowing/16SrIV-A.Brown, S.E., Been, B.O. & McLaughlin, W.A. (2006). Detection and variability of the lethal yellowing ...

'' (former name ''Myndus crudus'') which is native to Florida, parts of the Caribbean, parts of Australia and Central America. The only effective cure is prevention, i.e. planting resistant varieties of coconut palm and preventing a park-like or golf-course-like environment which attracts the planthopper. Some cultivars, such as the Jamaica Tall coconut cultivar, nearly died out because of lethal yellowing. Heavy turf grasses and similar green ground cover attracts the planthopper to lay its eggs there, and the nymphs develop at the roots of these grasses. The planthoppers' eggs and nymphs can pose a great threat to coconut-growing countries' economies, especially ones into which grass seeds for

golf course A golf course is the grounds on which the sport of golf is played. It consists of a series of holes, each consisting of a tee box, a fairway, the rough and other hazards, and a green with a cylindrical hole in the ground, known as a "cup". Th ...

s and lawns are imported from the Americas. It is not clearly understood how the disease was spread to

East Africa East Africa, Eastern Africa, or East of Africa, is the eastern subregion of the African continent. In the United Nations Statistics Division scheme of geographic regions, 10-11-(16*) territories make up Eastern Africa: Due to the historical ...

, as the planthopper ''Haplaxius crudus'' is not native to East Africa. The moss likely explanation is that it was imported with grass seed from Florida that was used to create golf courses and lawns in beach resorts. There is a direct connection between green lawns and the spread of lethal yellowing in Florida. Even so-called 'resistant cultivars' such as the

Malayan Dwarf Dwarf coconut is a range of varieties of coconut palm. The use of the word “dwarf” here does not refer to the tree's size, as it can reach heights of 50–100 feet which is certainly not a dwarf. Instead, the dwarf designation refers to the siz ...

or the Maypan hybrid between that dwarf and the Panama Tall were never claimed to have a 100% immunity. The nymphs of the planthoppers develop on the roots of grasses, hence areas of grass in the vicinity of palm trees is connected with the spread of this phytoplasma disease. The problem arose as a direct result of using coconut and date palms for ornamental and landscaping purposes in lawns, golf courses and gardens, together with these

grasses Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns and ...

. When these two important food palms were grown in traditional ways (without grasses) in plantations and along the shores, the palm groves were not noticeably affected by lethal yellowing. There is no evidence that disease can be spread when instruments used to cut an infected palm are then used to cut or trim a healthy one. Seed transmission has never been demonstrated, although the phytoplasma can be found in coconut seednuts, but phytosanitary quarantine procedures that prevent movement of coconut seed, seedlings and mature palms out of an LY epidemic area should be applied to grasses and other plants that may be carrying infected vectors. Beside coconut palm (''Cocus nucifera''), more than 30 palm species have also been reported as susceptible to lethal phytoplasmas around the globe.Howard, F. (1992). Lethal yellowing susceptibility of date palms in Florida. Principes, 36(4), pp. 217–222

References

{{reflist

External links

EPPO quarantine data sheet: Palm lethal yellowing
(pdf file)
Lethal Yellowing of Palm

Tropical agriculture Palm diseases

See also

References

External links