The use of molecular assays to identify plant pathogenic organisms vectored by biological control agents

The planthopper Prokelisia marginata Van Duzee (Homoptera: Delphacidae) has been considered for the biological control of the weed Spartina alterniflora Loisel (Poaceae) in Willapa Bay, Washington, U.S.A. Prokelisia marginata is a stenophagous phloem-feeding insect with the potential to transmit bacterial plant diseases that could be moved by less-specific vectors to other plant species. Initial assays with PCR primers that are putatively specific for phytoplasmas gave positive results in Spartina. However, subsequent analyses did not indicate the transmission of the pathogen by the planthopper. We sequenced the 16S ribosomal RNA (rRNA) gene of the bacterial species that gave positive results in PCR. Comparisons with sequences available in GenBank suggested that the positive results using the putatively specific PCR primers were due to the presence of such bacteria as Pseudomonas, Holomonas, Vibrio, and Acinetobacter. We did not find phytoplasmas in either Spartina or the planthopper P. marginata.