Transmission of phytoplasmas associated with Texas Phoenix palm decline (16SrIV-D) to Pritchardia pacifica by the planthopper Haplaxius crudus (Cixiidae) in Yucatan, Mexico

In the 1970's and 1980's "coconut lethal yellowing" (LY) was known as a single phytoplasma disease in Jamaica and Florida. The premature dropping of the nuts regardless of size, the blackening of new inflorescences and ascending yellowing of the leaves were considered as reliable diagnosis of LY. At the same time, in Florida, other palm species like Phoenix spp. Pritchardia spp. or Veitchia merrilii were affected by wilts showing similar symptoms. As phytoplasmas were diagnosed by electron microscopy in these species, they were also claimed to be affected by LY. Field evidence favored the planthopper Haplaxius (Myndus) crudus (Cixiidae) as a potential vector. Several trials to transmit LY by this insect started in Jamaica and Florida in the 1970s. After 10 years of research, transmission of LY disease to coconut (Cocos nucifera) was obtained in Florida, but not in Jamaica. In Tabasco State (Mexico) research conducted between 2006 and 2010 failed to obtain LY transmission by M. crudus despite 70,000 field collected insects placed on coconut palms in cages. Trials performed in 2011 in Yucatan showed that H. crudus collected in the field on various palm species (Thrinax radiata, Sabal spp., Washingtonia spp., coconut) were able to transmit a disease to Pritchardia pacifica but not to coconut palm. Phytoplasmas associated with the symptoms in Pritchardia were of the group 16SrIV-D, known as "Texas Phoenix palm decline". In fact it has recently been shown by PCR and sequencing that at least five subgroups of phytoplasmas, 16SrIV-A to F, occur in different palm species in the Caribbean area including west central Florida. The question as to which insect is associated which 16SrIV phytoplasma remains open. New trials are in progress. (Texte integral)