Evaluation continues

In the RNQP Questionnaire, PT and HR asked for deregulation arguing that the economic impact is acceptable with regards to the intended use. As a consequence, it is proposed to continue to apply the methodology on this pest, even though this pest is already listed in EPPO PM 4/8(2) Standard, with a particular attention to the economic impact.

Candidate

There is little literature on methods of transmission of grapevine fleck virus. It is known to be transmitted via plants for planting (the virus is tested in many certification schemes, and detected). It may be transmitted by an unknown vector. In Austria it was demonstrated that the distribution of GFkV within a vineyard was random, but not its distribution within the winegrowing regions. It suggests firstly (most likely explanation) the existence of a very mobile vector with low infectivity and secondly the minor importance of spreading by human activity (Gangl et al., 2011). In Italy, localization of GFkV-infected vines, which were uniformly distributed and often in isolation, suggested the role of aerial vectors rather than scale insects, in the spread of GFkV (Fortusini et al., 1996). In the absence of other information, it is considered that findings in new areas imply an introduction by the planting material. GFkV is often found in combination with other grapevine viruses in infected vineyards. As no vectors are specifically identified, experts concluded that plants for planting should still be considered as the main pathway in area where the pest is present.

Yes

Grapevine fleck disease is caused by various viruses, of which the most economically important is sometimes considered to be the Grapevine fleck virus (Jež, A et al., 2010). The disease is latent in European grapevines varieties (Vitis vinifera, L). Symptoms are expressed in Vitis rupestris (parent of many roostock hibrids) and consist of clearing of veins of third and fourth order, producing localized translucent spots. Leaves with intense flecking are wrinkled, twisted and may curl upward. Severe strains induce also varying degrees of stunting. Fleck is a ubiquitous disease reported from most viticultural countries in the world (Martelli, 2014). Due to its ubiquity and incidence, GFkV is taken into account in grapevine certification protocols all around the world. There are few references directly referring to yield or quality effects caused by GFkV by itself, it is usually found in association with other viruses. GFkV infection affects physiological processes, especially stomatal conductance (gs), whereas other processes are not significantly changed (Bota et al., 2014). Vidal blanc plants naturally infected by GLRaV-3 and GFkV at the same time had a 7% reduction in average berry weight, and titratable acidity levels were 14% higher compared to healthy plants (p<0.001) (Kovacs et al., 2001). The elimination of fanleaf (grapevine fanleaf nepovirus) plus GFkV induced increased vigour and fertility, although it did not improve grape or wine quality (Mannini et al., 1998). Despite being symptomless in Vitis vinifera, GFkV is thought to be partially associated to grapevine stunting and graft incompatibility (Cretazzo & Velasco, 2017). There are beneficial effects of eliminating GFkV from new clones in certification programs.

Minor on Vitis vinifera, medium on V. rupestris and probably medium on other species and their hybrids

No

Candidate

Impact is considered as acceptable on V. vinifera. Impact on other species and their hybrids [commonly used as rootstocks] are not.

candidate

Tests on Vitis indicators, ELISA testing and molecular tests, in the initial material of rootstocks are sufficient to ensure the absence in propagating material.