Transmission of Iris yellow spot virus by Frankliniella fusca and Thrips tabaci (Thysanoptera: Thripidae)

Thrips-transmitted Iris yellow spot virus (IYSV) (Family Bunyaviridae, Genus Tospovirus) affects onion production in the United States and worldwide. The presence of IYSV in Georgia was confirmed in 2003. Two important thrips species that transmit tospoviruses, the onion thrips (Thrips tabaci (Lindeman)) and the tobacco thrips (Frankliniella fusca (Hinds)) are known to infest onion in Georgia. However, T. tabaci is the only confirmed vector of IYSV. Experiments were conducted to test the vector status of F. fusca in comparison with T. tabaci. F. fusca and T. tabaci larvae and adults reared on IYSV-infected hosts were tested with antiserum specific to the nonstructural protein of IYSV through an antigen coated plate ELISA. The detection rates for F. fusca larvae and adults were 4.5 and 5.1%, respectively, and for T. tabaci larvae and adults they were 20.0 and 24.0%, respectively, indicating that both F. fusca and T. tabaci can transmit IYSV. Further, transmission efficiencies of F. fusca and T. tabaci were evaluated by using an indicator host, lisianthus (Eustoma russellianum (Salisbury)). Both F. fusca and T. tabaci transmitted IYSV at 18.3 and 76.6%, respectively. Results confirmed that F. fusca also can transmit IYSV but at a lower efficiency than T. tabaci. To attest if low vector competency of our laboratory-reared F. fusca population affected its IYSV transmission capability, a Tomato spotted wilt virus (Family Bunyaviridae, Genus Tospovirus) transmission experiment was conducted. F. fusca transmitted Tomato spotted wilt virus at a competent rate (90%) suggesting that the transmission efficiency of a competent thrips vector can widely vary between two closely related viruses.