Situation of Iris yellow spot virus in onion crops in the Netherlands: 2008 situation
In 2008, surveys were carried out in the Netherlands in onion crops (Allium cepa) in particular to study the extent of latent infections by Iris yellow spot virus (Tospovirus, IYSV – EPPO Alert List). A total of 660 onion plants were sampled from 14 fields across the Netherlands, and tested for IYSV. As no virus symptoms were observed in the field, leaf samples collected were either asymptomatic, showing thrips feeding damage or atypical necrotic lesions. IYSV-infections were detected in 13 out of the 14 studied fields, with 8 to 54% of the samples testing positive (on average 25.6%). The detection of IYSV could not be related to the presence of any symptoms. The results of this survey showed that IYSV was widespread in onion crops in 2008, mainly causing symptomless infections. The Dutch NPPO considers that that IYSV symptomless infections are likely to occur in other European countries, especially in those having similar growing conditions. So far, the main sources of infection in onion crops in the Netherlands remain unknown. All weeds and wild plants collected in the vicinity of infected onion fields tested negative. Research will continue to identify the primary source of virus infection at the beginning of the 2009 growing season.
The pest status of Iris yellow spot virus in the Netherlands is officially declared as: Present, in all parts of the area where onion is grown.
NPPO of the Netherlands, 2008-10. http://www.minlnv.nl/pd