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First Report on the Multiplication of Tomato Spotted Wilt Tospovirus in Tobacco Thrips, Frankliniella fusca

In Georgia, tomato spotted wilt tospovirus (TSWV) causes significant losses in peanut, tobacco, tomato, and pepper. Transmission of TSWV in Georgia primarily is by tobacco thrips (TT), Frankliniella fusca (Hinds), and western flower thrips, F. occidentalis (Pergande), with TT being the predominant vector species in peanut (2). TSWV must be acquired at the larval stage for the adult to transmit the virus. Detection of NSs (a non-structural TSWV protein present only following virus replication) in thrips by enzyme-linked immunosorbent assay (ELISA) is a reliable indicator that the virus had multiplied in the vector and thus the vector is competent to transmit TSWV. While this has been accomplished with F. occidentalis (1), information is lacking for F. fusca, the predominant vector in Georgia and other states in the Southeast. Thus, the nature of the TSWV-TT association was investigated and the proportion of transmitters in a field population determined in 1,436 individual adult TT collected from sticky cards positioned in selected peanut fields in south Georgia. Additionally, 650 larvae collected from volunteer peanut plants were reared to adults in the laboratory and the resulting 295 adult TT were individually evaluated by ELISA. Of those collected from the sticky cards, NSs was detected in 8% of the adult insects, indicating that the virus had multiplied in TT. NSs was not detected in control TT that had no access to the virus. Of the adult TT that emerged from larvae collected from volunteer peanuts, 6.1% were positive for NSs. Our study provides the first immunological evidence that TSWV multiplies in TT.

References: (1) M. D. Bandla et al. Phytopathology 84:1427, 1994. (2) J. R. Chamberlin et al. J. Econ. Entomol. 86:40, 1993.