Seasonal occurrence of thrips tabaci(Lindeman) and the incidence of necrotic streak disease caused by iris yellow spot virus (IYSV) on chinese chive Allium tuberosum

Abstract

We investigated the seasonal occurrence of Thrips tabaci (Lindeman), transmitter and viruliferous thrips of Iris yellow spot virus (IYSV), and the incidence of necrotic streak disease caused by IYSV in Chinese chive fields in Tochigi Prefecture, to establish a control system for the disease. The seasonal occurrence of T. tabaci had two peaks. The higher was in mid-June and the other was in mid-August to early September in 2007 and 2008. Transmitter and viruliferous thrips gradually increased from June, peaked between July and October and declined to low levels from December to May. The disease developed after the number of thrips increased, raising the incidence of transmitters and viruliferous individuals in the field. In contrast, symptoms were only observed from July to October and did not develop in new leaves or petioles after cutting plants off above the ground. Moreover, we found viruliferous individuals(1.9%) in the Chinese chive nursery in May 2008, and symptomless infection in the field, based on the detection of IYSV by DAS-ELISA. These results suggested that controlling the population density of thrips in mid-May prevented the development of the disease in Tochigi Prefecture.