This rapid assessment shows that: HSvd has a large host range and can cause disease in taxonomically diverse hosts, though symptomless infections are common. In the UK, hop is vulnerable to economic losses from HSVd infection. There have been no reports of the viroid in the UK. In Europe the first outbreak of HSVd in hop has been reported recently from Slovenia, where the infection was associated with classic disease symptoms of stunting and foliar damage. Pale fruit disease of cucumber is now rare in Europe though the disease has been reported and eradicated recently in Finland (Lemmetty et al 2011). The absence of an efficient HSVd vector limits spread of the viroid away from the initial site of infection, except when infected material is passed on to other premises. Consequently, avoidance of introduction of HSVd infected material through use of certified plants largely provides an efficient means of disease control, though crop monitoring is also important to mitigate introductions which may arise as very rare events. 

Risk of entry 

There is a moderate risk of HSVd entry. Most commercial hop growers in England are aware of the risks of the viroid from imported plants and use certified plant material, which have complied with import restrictions. There may be some risk of illegal importation of hop plants for planting by individuals for domestic or small scale use. The viroid could also be imported from infected grapevine or Prunus spp. 

Risk of establishment 

There is a high risk of establishment from imported ‘plants for planting’ since infected plants would be expected to maintain the infection. 

Economic impact

HSVd is evaluated to cause medium to large economic impacts mainly through potential losses to hop and cucumber production, though there is some uncertainty because of the unpredictability and insidious nature of the viroid. Endangered area Hop growing areas in England and glasshouse production growing cucumber. Premises involved with propagating Prunus and hedgerows.