Seeking the vectors of phytoplasmas infecting Trichilia havanensis Jacq. trees in Costa Rica

Phytoplasmas are plant pathogenic bacteria that infect a diversity of plants worldwide and are transmitted by Auchenorrhyncha (Hemiptera). A disease caused by phytoplasmas of 16Sr VII group (a ‘Candidatus Phytoplasma fraxini’ related strain) was detected in Trichilia havanensis Jacq. (Meliaceae) in the Central Valley of Costa Rica. This tree occurs naturally in the country, and it is commonly found in parks and roadsides. In order to determine the species of insects involved in the transmission of the disease, insects are being collected monthly with an inverted leaf blower pump around phytoplasma-infected trees at four sites. Auchenorrhynchan insects (mainly Cicadellidae) are sorted by morphospecies and placed on individual potted T. havanensis trees inside aphid-proof net sleeves for a 3-days inoculation access period (IAP). Afterwards, these insect samples are tested by PCR to determine presence of phytoplasma in their bodies, and trees are kept in a greenhouse for future testing (6 and 12 months after IAP). One hundred twenty-two transmission tests (trees) have been done with 72 different morphospecies, as of May 2022. Preliminary, PCRs with DNA obtained from insect bodies from these assays yielded positive results for phytoplasma detection in at least one morphospecies, Scaphytopius sp. (3 out of 12 samples). The amplicon sequence obtained from one of these insect samples corresponded to the same phytoplasmas group detected in T. havanensis. Thus far, the data suggest at least one possible candidate vector species, Scaphytopius sp. Corresponding transmission assays to test vectorial capacity are in progress.