Potential of Prokelisia spp. as biological control agents of English cordgrass, Spartina anglica

Spartina anglica, English cordgrass, has been isolated from North American herbivores since its 19th century amphidiploid hybrid origin in England. We found a population of this estuarine plant, introduced to Puget Sound, Washington, to be highly vulnerable to Prokelisia spp. planthoppers from California. More than 90% of plants died in greenhouse culture with high planthopper densities, while <1% died at the very low hopper densities of the control. English cordgrass invades the open intertidal mud of Pacific estuaries of North America, jeopardizing native flora and fauna of saltmarshes. This invasive plant alters the hydrology of marshes by accreting sediment. If intolerance to Prokelisia spp. in the field correlates with that in the greenhouse, biological control by this planthopper could contribute to management of cordgrass populations sensitive to this insect. Prokelisia spp. are stenophagous and pose little apparent threat to other plant genera. Neither the biological basis nor the inheritance of cordgrass vulnerability to the Prokelisia spp. are known. If genetic variability in vulnerability to this planthopper exists within the population of S. anglica, care would be needed to prevent increase of more resistant plant genotypes as a result of introduction of the insect.