Book Description

Peppermint, Mentha piperita 'Black Mitcham' was established as a host for tomato spotted wilt virus-impatiens serotype (TSWV-I). TSWV-I infection of peppermint, initially observed in a research greenhouse (Corvallis, OR), included stunting and downward curling of leaves accompanied by bronzing, and occasionally tip necrosis. Young leaves appeared either symptomless, deformed, or pale even under high nitrogen conditions. Older leaves had sunken, brownish-grey lesions. Bright yellow mottling was observed on newly mature deep green leaves. A begonia isolate of TSWV-I was transmitted to peppermint both mechanically and by western flower thrips, Frankliniella occidentalis (Pergande). Symptoms of TSWV-I infection were similar although only a faint yellow mottling was produced and only under cool temperatures (15°C). ELISA detection of virus distribution throughout the plant indicated infection was systemic. Bulked groups of thrips (5 thrips/sample) also tested positive for TSWV-I using ELISA. Transmission efficiency of 4, 6, 8, and 10 day old thrips adults given acquisition sources during the entire nymphal stage varied from 0-40% for thrips tested in pairs and 0-20% for single thrips (based on a 12 hour access feeding period). Adults 2 days old failed to transmit the virus. Western flower thrips exposed to TSWV-I had reduced survival and reproductive potential and slower development rates than unexposed thrips. Virusexposed thrips were 1.4 times as likely to die than unexposed thrips on a given day. Both individual and population reproductive potentials were significantly lower. Preoviposition period was extended in virus-exposed thrips. Development time from second instar to adult was 15% longer for virus-exposed thrips. This is the first report of altered population parameters in western flower thrips exposed to TSWV-I.