Scientific Opinion on the risk to plant health posed by Chrysanthemum stunt viroid for the EU territory, with identification and evaluation of risk reduction options

The Panel on Plant Health conducted a pest risk assessment for Chrysanthemum stunt viroid (CSVd) and identified and evaluated risk reduction options, particularly those listed in Council Directive 2000/29/EC. Three entry pathways were identified, with plants for planting being the most important and rated as moderately likely. CSVd is recorded in some EU Member States with a limited distribution and is regulated on chrysanthemum; host plants are widely cultivated in greenhouses and outdoors. Therefore, establishment is very likely. Short-distance spread within a crop is likely, whereas short-distance spread between different species is unlikely to moderately likely. For vegetatively propagated species, in the absence of an efficient certification system, long-distance spread is very likely and a major impact would be expected on chrysanthemum, with associated yield and quality losses. However, under the existing certification scheme for chrysanthemum plant propagation material, the probability of spread through infected cuttings is largely reduced and the direct consequences of viroid outbreaks are expected to be minor. Minimal impact is predicted for other ornamental hosts and a minor impact for solanaceous vegetable crops. The indirect effects of CSVd are considered to be limited, with the exception of eradication. Risk reduction options addressing the sanitary status of the propagation material are likely to be the most effective and feasible. These include the current EU measures, as well as a statutory certification system with associated statutory import requirements or, failing that, but potentially less effective, the use of voluntary industry standards. It is difficult to disentangle the benefits of the current legislation from those of the industry-developed chrysanthemum certification system. The high efficacy of current measures is supported by the absence or limited presence of CSVd in the EU and by the limited number of interceptions and findings. Possible improvements to current measures are described and uncertainties discussed.