Occurrence of Tomato spotted wilt virus (TSWV), seasonal abundance of thrips vectors, and evaluation of TSWV control measures in dahlia fields

Spotted wilt disease caused by Tomato spotted wilt virus (TSWV) is one of the most important diseases affecting the production of bulbs and cut flowers of Dahlia variabilis in Japan. In Nara Prefecture, the main vector species of TSWV were thrips Frankliniella intonsa and Frankliniella occidentalis. The number of F. intonsa and F. occidentalis captured using blue sticky traps increased in late June and mid-May, and peaked in early July and late May to early June, respectively. TSWV viruliferous F. intonsa and F. occidentalis occurred throughout almost the entire production period in bulb production fields. TSWV might be transmitted by thrips, and the infection rates in dahlias reached up to 80% in a cut flower field. However, the use of insect proof nets greatly decreased the infection rates. In addition, the removal of dahlias with TSWV symptoms effectively decreased the rates of diseased plants. To prevent the spread of TSWV, it is important to prevent invasion of thrips using physical barriers. In addition, removal of the source of infection is an effective way to reduce the occurrence of disease.