Analysis and identification of insect vectors causing phytoplasmic diseases in Florida

Lethal Yellow (LY) and Texas Phoenix Palm Decline (TPPD) are diseases caused by phytopathogenic bacterium that threaten a variety of economically important palm species in the southern U.S. Both bacteria are classified as phytoplasmas, which are symbiotic bacteria that lack a cell wall. These pathogens are transmitted to naïve plant hosts by phloem feeding insect vectors. There are two possible phloem feeding insect suspects; leafhoppers (Cicadellidae) and planthoppers (Fulgoridae). From these there have been three possible suspects in Florida and Texas; Cixiidae (Haplaxius crudus which has been confirmed as a positive for LY and negative for TPPD), Flatidae spp., and Derbidae spp. In most locations where these pathogens occur, the vector complex has not yet been identified, thus management of this disease is difficult. In this study, insects were collected off infected trees and placed on an artificial feeding media (feeding sachet). Nested polymerase chain reaction (PCR) assays were used to detect phytoplasmas from various symptomatic palms and insects. A product was obtained from 9 symptomatic palms and from 8 of 126 insects when products were amplified using nested polymerase chain reaction (PCR) employing LY group-specific 16S rRNA primer pair LY16Sf2/LY16-23Sr2. Restriction fragment length polymorphism (RFLP) analysis of nested PCR products revealed distinct phytoplasma strains.