Abstract

In early 2003, 4-year-old pyrethrum crops in north-west Tasmania were surveyed for the presence of Tomato spotted wilt virus (TSWV), Beet western yellows virus (BWYV), Cucumber mosaic virus (CMV), Tomato aspermy virus (TAV), various members of the genera Potyvirus and Carlavirus, and Chrysanthemum stunt viroid (CSVd). Of these, only TSWV was detected by enzyme linked immunosorbent assay and infection confirmed by reverse transcription polymerase chain reaction. Most (18/21) of the crops planted in 1999 contained plants symptomlessly infected with TSWV, with a mean incidence of 2.6% (range 0–11.3%). In comparison, less than half of 1-year-old crops were affected by TSWV and the mean incidence of infection was only 0.1% (range 0–0.5%). Examination of the spatial distribution of TSWV infected crops (irrespective of age) showed crops in the Central Coast region had a significantly higher mean incidence of TSWV (3.1%) than those in the Devonport (0.2%) and Burnie/Wynyard (0.2%) regions.