Transmission mechanisms of Nosema empoascae (Microspora: Nosematidae) in Empoasca fabae (Homoptera: Cicadellidae)

Four experiments investigating horizontal and vertical transmission mechanisms of the microsporidium Nosema empoascae, in a population of the potato leafhopper, Empoasca fabae, were conducted. Transovarial transmission was the only route of transmission demonstrated experimentally. Transmission on the egg surface was unlikely. Spores were not present in fecal droplets, and in laboratory experiments the microsporidium could not be transmitted horizontally, either by contact or in venereal transmission experiments. Thus, this microsporidium persists primarily, if not exclusively, by transovarial transmission in the leafhopper populations. If horizontal transmission occurs, it occurs at a very low rate through an as yet undetermined mechanism. The ramifications of transovarial transmission as an exclusive mechanism are discussed.