|Brussels, 13th January 2016
Recommendation of the Working Group on the Annexes of the Council Directive 2000/29/EC – Section II – Listing of Harmful Organisms as regards the future listing of Verticillium dahlia Kleb. 1
Current regulatory status
V. dahliae is a harmful organism currently regulated in the Annex IIAII of Council Directive 2000/29/EC on plants of hops (Humulus lupulus only). Its other numerous hosts are not regulated.
Hop plants are not included in any Marketing Directives, although V. dahliae is regulated in some marketing directives as a RNQP for many other hosts.
Specific requirements are laid down in Annex IVA, sections I and II, as regards the introduction and movement of plants for planting into and within all EU Member States; and Annex VAI and Annex VBI as regards obligations for plant health inspection before being permitted to enter the EU.
Identity of the pest
V. dahliae is a single taxonomic entity and sensitive and reliable methods exist for its detection and identification. V. dahliae is a highly polyphagous pathogen, affecting, overall, 400 cultivated and non-cultivated plant species. It has the ability to continuously widen its host range and develop races/pathotypes that can overcome host resistance or be more virulent on known hosts and host cultivars.
Distribution of the pest
The pathogen is currently present in most EU Member States and in many hosts. It also occurs in all MSs where hops are grown. However, V. dahliae does not appear to be significant in causing hop wilt, by itself. Its listing on hops may be a result of confusion that existed in the past between V. dahliae and V. albo-atrum.
Potential for establishment and spread in the PRA area
V. dahliae is a highly polyphagous soil-borne pathogen and is present in most parts of the risk assessment area. Following establishment, the pathogen has the potential to spread by both natural (wind, water) and human-assisted means (movement of infected host planting stock, particularly asymptomatic plants or by infested soil).
Pest can infect hop plants and infection can be symptomless in growing plants and hence be harvested and moved. EFSA states host plants for planting can be one of the pathways for the introduction into, and spread within, new areas. Also there are no reports available on the impacts caused by the pathogen as a result of the intended use of infected host plants for planting.
On decomposition, infected material will decompose and release viable microsclerotia into the soil which are known to survive at least 10 years and be spread by soil movement.
Potential for consequences in the PRA area
Movement of infected host plants for planting, especially asymptomatic plants, and seeds can introduce the pathogen (and its highly virulent races/pathotypes) into new areas. Hop is susceptible to V. dahliae, however it is considered of minor importance compared with V. albo-atrum (Pegg and Brady, 2002) in causing hop wilt disease. Verticillium wilt of hops is caused by the hop-infecting strains of V. albo-atrum (these strains are now referred to as being within V. nonalfalfae).
V. dahliae is not known to cause any environmental consequences in wild hops in hedgerows or other natural areas in the EU. Application of integrated management strategies combined with disease risk evaluation (assessment of the available soil-borne inoculum, determination of races/pathotypes present in the site, field cropping history) may reduce the impacts of Verticillium wilt in the risk assessment area.
However, the requirement for absence of symptoms does not always ensure absence of the pest, mainly because of the possibility of symptomless contamination of planting material. Certified planting material is commercially available, which is visually inspected for hop wilt and is derived from nuclear stock that has been tested and found free from any Verticillium species.
The Working Group believes that V. dahliae does not meet the definition of a Union Quarantine Pest under the Plant Health proposal (COM(2013)267final), as it is not present in a “limited part” of the EU, or that its presence is only “scarce, irregular, isolated and infrequent”. Eradication measures are also not officially required in hop gardens.
At the same time, it is difficult to distinguish the impact caused by each species of Verticillium nonalfalfae and V. dahliae.
Given that the main pathway of distribution is represented by plants for planting, the difficulties in distinguishing the species apart, and the risk involved, the Working Group suggests listing V. dahliae as Regulated Non-Quarantine Organism for hops (Humulus lupulus).
The Pest Risk Assessment of EFSA does not need to continue.