Transmission characteristics and host range of the clover yellow edge agent

Abstract

A disease of clover, designated as clover yellow edge (CYE), was transmitted by Aphrodes bicinctus (Schrank) but not by the leafhoppers Scaphytopius acutus (Say), Macrosteles fascifrons (Stal), Agallia constricta Van Duzee, and Agallia quadripunctata Prov. or a Cercopid sp. Transmission by A. bicinctus, given various acquisition access periods on infected clover as nymphs, increased from 29% for 1 day to 67% for 14 days for females and from 42% for 1 day to 72% for 14 days for males. When leafhoppers were given similar acquisition access periods as adults, transmission ranged from 5% for 1 day to 24% for 14 days for females and from 25% for 1 day to 33% for 14 days for males. Inoculative female leafhoppers, given inoculation access periods ranging from 0.5 h to 96 h, began transmitting with 1-h feeds (29%) and reached a maximum with 96-h feeds (88%). Inoculative males began transmitting with 8-h feeds (50%) and reached a maximum with 48-h feeds (83%), the longest time tested. The average preinfective period for female and male leafhoppers tested individually was 42.2 days and 40.1 days, respectively. Once an insect became inoculative, it continued to transmit until death.Of the 31 plant species in 12 families tested as hosts of the clover yellow edge agent (CYEA). 15 species in 6 families developed symptoms. The most commonly observed symptoms were chlorosis or yellowing of leaf margins and reduction in the size of flowers and leaves. Aphrodes bicinctus transmitted CYEA to clover from eight of eight infected plant species tested as source hosts.