Occurrence of the Onion Thrips, Thrips tabaci（Thysanoptera: Thripidae）at Onion Fields in Winter

Abstract

Occurrence of the onion thrips, Thrips tabaci Lindeman, was examined from late December to late May at onion fields with three different cropping types, early, middle, and late seasons, in Kagawa Prefecture, western Japan. In the early season onions, survival of adults, larvae and newly hatched larvae of T. tabaci was observed on onion plants during winter and their occurrence was increased from April. In the middle season onions, T. tabaci of all developmental stages were found from late April. In the late season onions, newly hatched larvae increased from early March in the field where T. tabaci adults had occurred. On the other hand, no such increase of newly hatched larvae was observed in the field where fewer adults had existed. Oviposition of adults on onion seedlings was also examined in the laboratory and field conditions in March. The newly hatched larvae from onion seedlings were found at 10°C and 20°C in the laboratory and in the field.