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CANADIAN FOOD INSPECTION AGENCY  
59 Camelot Drive  
Ottawa, Ontario  
K1A OY9  
Tel: 613 -225-2342    FAX: 613 -773-7204 RMD -13-05  
 
, 2014  
  
Title:  Pest Risk Management Document – Response to the Detection of Grapevine Virus A 
and Gra pevine Virus B  
 
 
 
 
Preface  
 
As described by the International Plant Protection Convention (IPPC), Pest Risk Analysis 
(PRA) includes three stages: initiation, pest risk assessment and pest risk management. 
Initiating the PRA process involves identifying pests and pathways of concern and defining 
the PRA area. Pest risk assessment provides the scientific basis for the overall management 
of risk. Pest risk management is the process of identifying and evaluating potential mitigation 
meas ures which may be applied to reduce the identified pest risk to acceptable levels and 
selecting appropriate measures.    
 
This Risk Management Document (RMD) includes a summary of the findings of a 
pest risk assessment and records the pest risk management p rocess for the identified 
issue.  It is consistent with the principles, terminology and guidelines provided in the 
IPPC standards for pest risk analysis which may be found at https://www.ippc.int/ . 
 
 
 
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Table of Contents  
 
1.0 Executive Summary  ................................ ................................ ................................ .............  3 
2.0 Purpose  ................................ ................................ ................................ ................................ . 3 
3.0 Scope  ................................ ................................ ................................ ................................ .... 3 
4.0  Definitions, Abbreviations and Acronyms  ................................ ................................ ..........  4 
5.0  Background  ................................ ................................ ................................ ..........................  4 
6.0  Pest Categorisation Summary  ................................ ................................ ..............................  5 
6.1  Pest Identities  ................................ ................................ ................................ ...................  5 
6.1.1   Grapevine Virus A (GVA)  ................................ ................................ ..........................  5 
6.1.2   Grapevine Virus B (GVB)  ................................ ................................ ...........................  5 
6.2  Distribution ................................ ................................ ................................ .......................  5 
6.2.1   Grapevine Virus A  ................................ ................................ ................................ ... 5 
6.2.2   Grapevine Virus B  ................................ ................................ ................................ ... 6 
6.3 Means of Dispersal and Spread  ................................ ................................ ........................  6 
6.4 Symptoms  ................................ ................................ ................................ .........................  6 
6.4.1  GVA  ................................ ................................ ................................ ..........................  6 
6.4.2  GVB  ................................ ................................ ................................ ..........................  6 
6.5  Probability of Establishment and Spread  ................................ ................................ .........  7 
6.6  Impacts  ................................ ................................ ................................ .............................  8 
7.0 Pest Risk Management Considerations  ................................ ................................ ................  8 
8.0 Recommendation and Rationale  ................................ ................................ ..........................  9 
9.0 References  ................................ ................................ ................................ ..........................  10 
10.0  Endorsement  ................................ ................................ ................................ ......................  12 
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1.0 Executive Summa ry 
 
Grapevine Virus A (GVA) and Grapevin e Virus B (GVB) are closely associated with two 
grapevine diseases that are regulated in  Canada. Both viruses are members of the genus Vitivirus  
and are transmitted primarily through propa gation and grafting. I nsect vectors, including certain 
scale insect species, are  also capable of spreading the virus within a vineyard.  
 
Grapevine Virus A and GVB are known to be present in the United States  (U.S.)  and Europe, as 
well as many other countries. GVA has been under offic ial contro l in British Columbia (B.C.) 
since 200 0, when it was  detected on propagative stock.  Through audit sampling, GVA  was then 
detected in B.C. in 2009  and GVB  was detected in Ontario in 2010. Following  these detections, 
the Canadian Food Inspection Ag ency ( CFIA ) conducte d targeted surveys in 2011 (GVA)  and 
2012  (GVB)  to determine  the distribution  of these viruses in Canadian vineyards.  A CFIA Pest 
Categorisation outlined that, although GVA and GVB can potentially cause economic damage to 
industry by red ucing the productivity of specific grape cultivars,  there are other considerations 
that impact the regulatory status of these viruses in Canada. These considerations include:  
 
 The distribution of GVA and GVB within Canada;  
 The likelihood of successful erad ication of these viruses ; 
 The possibility of effectively managing these pests through best management practices;  
 The economic costs of regulatory action to be borne by both taxpayers and the industry; 
and 
 The current Canadian regulatory framework.  
 
Based o n an analysis of these considerations, this document presents a recommendation to 
deregulate the diseases with which these viruses are associated.  
 
 
2.0 Purpose  
 
The purpose of this document is to seek stakeholder input into the CFIA recommendation to 
deregulate  GVA, GVB and their associated diseases in Canada.  
 
 
3.0 Scope  
 
This Risk Management D ocument examines the phytosanitary risks associated with GVA a nd 
GVB and presents a regulatory recommendation  for consideration.  
 
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4.0  Definitions, Abbreviations and Acronyms  
 
Definitions for terms used in this document can be found in the Plant Health Glossary of Terms 
at http://www.inspection.gc .ca/plants/plant -
protection/directives/glossary/eng/1304730588212/1304730789969  or the IPPC Glossary of 
Phytosanitary Terms at www.ippc.int  
 
 
5.0  Background  
 
Grapevine Virus A has been under official control in B.C. since 200 0, when it was detected on 
propagative stock. GVA  was then detected again in B.C.  (2009)  and GVB  in Ontario  (2010) , as a 
result of audit sampling.   
 
Following  these detections, the Canadian Food Inspection Agency (CFIA) conducted targeted 
surveys in 2011 (GVA) and 2012  (GVB)  to determine the distribution of these viruses in 
Canadian vineyards. These surveys indicated a widespread  very low level presence of GVA  in 
B.C. and GVB  in Ontario .   
 
Grapevine Virus A is closely  associated with  Kober stem groov ing diseas e and GVB is closely 
associated with  corky bark disease. These diseases , which are regulated quarantine pests in 
Canada,  can cause decreased lifespan in grapevines  as well as a reduction in fruit quality  and 
yield , resulting in economic losses in  susceptible grape varieties .  
 
While it has not yet been proven that GVA and GVB are the causal agents of the regulated 
diseases, they are so closely associated that it is very difficult to regulate the diseases without 
regulating the viruses. Therefore t he CFIA has been de facto  regulating GVA and GVB since 
they were originally linked to the regulated diseases.  
 
Grapevine Virus A and GVB have a  worldwide distribution and both are present in  the U.S. and 
France. These countries are the two main sources for  grapevine propagative material for  Canada 
and phytosanitary requirements are currently in place to mitigate the export of GVA and GVB 
infected plants into Canada from both the U.S and France.  
 
In France, GVA and GVB are considered to be secondary viruses  within the scope of their 
grapevine export certification program; therefore up until 2012, only a small percentage of the 
plants exported to Canada were actually tested by France for the presence of these viruses. 
Because France is a major source of grape vines for Canada, it is possible that infested grapevines 
have unknowingly entered the country  prior to 2012 . With this in mind,  and taking into account  
the detections of the pest s in Canada,  the CFIA is re-evaluating the regulatory status of GVA and 
GVB i n Canada.   16 June 2014    RMD 13 -05  
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6.0  Pest Categorisation Summary  
 
The CFIA’s Pest Categoris ation for GVA  and GVB  was completed in July 2013 .  The following 
sections present the highlights of the categorisation . 
 
 6.1  Pest Identities  
 
Grapevine Virus A and GVB are both membe rs of the genus Vitivirus , which consist of 
flexous, non -enveloped,  filamentous particles with a length and diameter of 725 -785 nm 
by 12 nm. Virus particles consist  of a single, linear, positive sense, RNA genome (du 
Preez et al , 2011). Both GVA and GVB ar e phloem -associated viruses, replicating in the 
cytoplasma of host cells in association with  membranous vesicles (du Preez et al , 2011).  
  
  6.1.1  Grapevine Virus A (GVA)  
 
  Synonyms: Grapevine stem pitting associated virus (GSPaV) (Credi et al , 2010;  
  Conti et al , 1980) , Grapevine (A) trichovirus (CABI 2013), Grapevine corky bark  
  virus (CABI, 2013) .  
 
  Common names: Grapevine stem pitting disease, Grapevine closterovirus (CABI,  
  2013), Kober stem grooving, Shiraz Disease  
 
  6.1.2  Grapevine Virus B (GVB)  
 
  Synonym: Grapevine B trichovirus (Brunt et al n.d.)  
 
  Common name: Rough bark, Corky bark  
 
  
 6.2  Distribution  
 
  6.2.1   Grapevine Virus A   
 
 Grapevine Virus A has a worldwide distribution, having been reported from 
 Europe, Asia, the U.S. (California,  Washington, Michigan, Missouri and New 
 York) and South America, the Middle East, New Zealand and Australia, where it 
 is widely present in symptomle ss grapevines. GVA was first detected in B.C. in 
 2000, then again in 2009 and 2011.  
 
 
 
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  6.2.2  Grapevine Virus B  
 
 Grapevine Virus B has a worldwide distribution, having been reported from 
 Australia, the U.S. (California,  Washington, Michigan and New York), Europe 
 (Italy, France, Gr eece, Portugal, Spain), Russia, South America, the Middle East , 
 Asia, In dia, South Africa, among others  (Osman and Rowhani , 2008; Bosci a et al , 
 1993). GVB was first detected in Ontario in 2010  and then again in 2012.  
 
  
 6.3 Means of Dispersal and Spread  
 
 Both GVA and GVB are transmitted primarily through propagat ion and grafting, and 
transmission  can occur from rootstock to scion and vice ve rsa. Neither nematode nor seed 
transmission has been reported for ei ther GVA or GVB, although field spread has been 
observed for both viruses and both are transmitted by severa l scale insect species 
(Constable and Rodoni , 2011).   Many of the species of scale insects that are known to be 
capable of transmitting both GVA and GVB are also known to be present in Canada . 
Mechanical transmission through tools and equipment has also be en observed.  
 
 
 6.4 Symptoms  
 
  6.4.1  GVA  
 
On many commercial cultivars, especially white grape varieties, GVA is 
symptomless . Some symptoms that have been observed on susceptible grape 
varieties include distinct longitudinal grooves along the rootstock, a  progressive 
reduction in fruit yield over a few years, and then death of the plant. GVA has 
also been linked to ‘Shiraz Disease’ which affects the Shiraz variety of grape.  
The Shiraz variety of grape is known to be one of the most virus -susceptible 
varie ties of grape.  
 
  6.4.2  GVB  
 
Grapevine Virus B is clearly associated with symptomatic LN33 hybrid grapevine 
plants  (the indicator for Corky bark disease), strongly suggesting that GVB is the 
cause of corky bark  (Goszczynski , 2010).  Corky bark affect s only grafted vines; 
while a rootstock may carry the disease, the rootstock itself would remain 
symptomless. Once material is grafted onto infected but symptomless material, 
the scion becomes infected and may die, while the rootstock remains healthy. On 
many com mercial cultivars, GVB is symptomless. Some symptoms that have been  16 June 2014    RMD 13 -05  
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observed include growth retardation at leaf shoots, dieback of shoot s, soft and 
rubbery canes with longitudinal cracks at the base, an abnormal corky overgrowth 
of bark along with longit udinal cracks on canes, deep pitting and grooving of the 
wood cylinder, and characteristic internodal swelling due to enlargement of 
phloem tissues  (Rosa et al , 2011; Whattam , 2001).  
 
Many commercial cultivars remain symptomless or show only a mild reducti on in 
vigour when  affected by GVB ( Whattam , 2001). However, with certain 
scion/ rootstock combinations,  corky bark can be a major disease (Whattam , 
2001). On some cultivars, such as Cabernet Franc  and Gamay in California, GVA 
and GVB  induce  growth retardati on at leaf burst or dieback of a few  shoots 
(Whattam , 2001).  
 
 
 6.5  Probability of Establishment and Spread  
 
Grapevine Virus A has been  under o fficial control in Lillooet, B .C. as a result of the 
detection of the virus in the grape cultivar  Limberger in 2000. GVB is not currently under 
official control. The  viruses would be potential candidates for official control only if their 
distribution within Canada  was known and determined to be relatively limited. Imported 
grapevine materi al infected with GVA and G VB, and their associated diseases, has been 
detected by the CFIA Center for Plant Health  numerous times on imported material over 
the past four decades, indicating not only the widespread presence of these viruses in  the 
countries from which Canada imports  grapevine material, but also the potential of their  
repeated introductions via the plants for planting pathway.   
 
Grapevines infected with GVA or GVB may not exhibit any symptoms of infection and 
may show only a mild reduction in vigor.  In addition to be ing graft -transmissible, both 
viruses are vector -borne and can spread slowly within a vineyard if vectors are present. 
The overall distribution of these viruses within Canada remains unknown, but evidence 
suggests  they are more widely distributed than repo rted.   
 
Grapevine Virus A and GVB  viruses are already known to be present at low levels in 
vineyards in B.C. and Ontario respectively and therefore would be expected to survive 
wherever cultivated and wild host Vitis species grow in Canada, in particular,  regio ns 
with commercial production. Based on Statistics Canada (2012) data, Canada has a total 
of 29,119 acres of table and wine grapes with the major production areas being B.C., 
Ontario, Quebec and Nova Scotia.   
 
As with other  plant viruses, there is no  effective treatment  once either GVA or GVB is 
present in a vineyard. Disease management depends upon the use of certified, healthy, 
virus -free stock. As both viruses are vector transmitted, effective disease management of  
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GVA and GVB may include vector  control, removal of infected plants and disinfection of 
vineyard tools  and equipment .  
 
 
 6.6  Impacts  
 
Both GVA and GVB can result in economic losses due to a decreased lifespan of the  vine 
or reductions in either yields and/or fruit quality in certain s usceptible grapevine varieties, 
especially  if present in mixed infections w ith other grapevine viruses. In Italy, crop losses 
ranging from 5 -22% in wine grape cultivars  have been attributed to GVA. GVA has also 
been identified as the possible cause of decline and death of table grapevines that are also 
infected with  leafroll disease  (Martelli 1993). Constable and Rodoni (2011) report that up 
to 50% yield losses have been  reported in susceptible varieties infected with GVA. They 
also reported yield reduction s of up to  70% in susceptible varieties affected by corky bark 
associated with GVB.  It should be noted that these losses have been recorded in areas 
where there was a high vector prevalence.  
 
The total farm gate value of grapes in Canada is estimated at ov er $112.6 million.  A 
2013 report on  the Canadian grape and wine industry revealed that the industry 
contribute s annually approximately $6.8 billion dollars in economic impact to the 
Canadian economy  (Pasacreta, F. et al, 2013) .  
 
The impa ct of GVA and GVB is highly variable and dependent on many factors 
including  susceptibility of the grapevine variety, the combination of rootstock and scion, 
varying levels of  pathogenicity of virus strains, the presence of other viruses and climatic 
condi tions . These factors make  it difficult, if not impossible, to estimate the overall 
impact of either virus on the Canadian  viticulture industry.  
 
  
7.0 Pest Risk Management Considerations  
 
 Grapevine Virus A and GVB are present in the U.S and are only regul ated within 
state virus certification programs and grapevine import certification programs.  
 
 Canada’s only export market for grapevines is the U.S. In order to export to the U.S. , 
grapevines must have been produced in accordance with a grapevine export 
certification program which ensures freedom from various grapevine diseases 
including GVA and GVB.  
 
 Prior to 2012, a very small percentage of French grapevines were tested for GVA and 
GVB before  being certified for export to Canada. As a result, it is very l ikely that the 
viruses have entered Canada from French grapevines in the past and are now present 
in Canada.  16 June 2014    RMD 13 -05  
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 These organisms could meet the International Plant P rotection Convention definition 
of quarantine pests if they were not widely distributed within  Canada and were 
placed under official control  
 In Canada, GVA and GVB could be managed through domestic certification 
programs.  
 
 
8.0 Recommendation  and Rationale  
 
The CFIA must consider several factors when determining the appropriate regulatory response to 
the detection of a plant pest in Canada. In the case of GVA and GVB, the combination of several 
factors has resulted in the recommendation  to deregulate  the diseases  with which these viruses 
are associated : Kober stem grooving disease and Corky bark dis ease. This section presents a 
summary of those factors.  
 
1. The potential distributi on of GVA and GVB within Canada:  
 
- These  viruses and their associated  diseases have been detected in two 
significant grape growing regions in Canada.  
 
- In order to eradicate th ese viruses from Canada,  an extensive national pest 
survey would be required and all material found to be infected would need to 
be destroyed.  
 
- GVA and GVB are widespread in France and have been detected  through 
import audits of  grapevine material several  times over the last decade , 
suggest ing that these diseases cou ld be widespread throughout grape growing 
regions of Canada.  
 
2. The possibility of effectively managing these pests through best management practices : 
 
- The transmission of these diseases can be p revented through management 
practices, including pest control against potential insect vectors  and sourcing 
new vines from certified virus -free material . 
 
3. The likelihood of successful eradication of these viruses:  
 
- Given the wide distribution of grapevine material that has been imported from 
origins known to have these diseases, the probability of locating and 
destroying all infected material within the country is very low.  
 
- Previous regulatory mechanisms in place to control movement and 
distri bution of GVA  infected material  in B.C. were limited in success  due to a  16 June 2014    RMD 13 -05  
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combination of CFIA resource constraints and lack of industry compliance.  
 
4. The economic costs of regulatory action to be borne by both taxpayers and the ind ustry:  
 
 Official control of infected  material would require a very significant resource commitment from 
the CFIA and the industry.  
- The only effective means of eradicating these diseases is through destruction 
of infected material – this would be a significant economic cost to the 
industry.  
  
5. The curren t Canadian regulatory framework:  
 
- Canada does not currently have a regulatory framework that supports the 
regulation of pests on imported material when the pest is present and not 
under official control in Canada. Therefore complete deregulation  is required 
unless eradication or effective official control is achieved.  
 
Under this recommendation, th e viruses and diseases would continue to be managed through the 
grapevine export certification program to ensure that Canadian grapevine propagative ma terial 
that is exported remains pest -free. The CFIA does not have a regulate d non quarantine pest 
framework;  therefore it cannot regulate imported material for pests that occur in Canada. This 
means that the CFIA could no longer require freedom from these diseases on imported 
grapevines.  The responsibility would lie with the importer to source their material from exporters 
who are able to provide certified virus -free propagative material.  
 
 
9.0 References  
 
Boscia D, V Saino, A Minafra, S Namba, V elicia, MA  Castellano, D Gonsalves and GP 
Martelli.1993. Properties of a filamentous virus isolated from grapevines addected by corky 
bark. Arch  
Virol 130:109 -120. 
 
Brunt, AA, K Crabtree, MJ Dallwitz, AJ Gibbs, L Watson and EJ Zurcher (eds.) (1996 onwards).  
`Plant V iruses Online: Descriptions and Lists from the VIDE Database. Version: 20th August  
1996.' [http://biology.anu.edu.au/Groups/MES/vide/ ] 
 
CABI 2013. Grapevine Virus A. In: Crop Protection Compendium. Wallingford, UK: CAB  
International. [www.cabi.org/cpc ] 
 
Constable, F and B Rodoni. 2011. Fact Sheet. Rugose Wood - associated viruses. Department of  
Primary Industries. Australian Government Grape and Wine Research and Development  
Corporation.  16 June 2014    RMD 13 -05  
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Conti M, RG Milne, E Luisoni and G Boccardo. 1980. A closterovirus fro m a stem -pitting -
diseased  grapevine. Phytopathology 70(5):394 -399. 
 
Credi, R, F Terlizzi, C Lanzoni, L Martini, S Borsari and E Pasqualini. 2010. Planococcus  
ficus transmits two vine viruses. La cocciniglia farinosa trasmette due virus della vite. 
Informat ore Agrario 66(33): 65 -68. 
 
du Preez, J, D Stephan, M Mawassi and JT Burger. 2011The grapevine -infecting vitiviruses, 
with particular reference to grapevine virus A. Arch Virol. 150:1495 -1503.  
 
Goszczynski, D. 2010a. Divergent molecular variants of Grapevi ne virus B (GVB) from corky 
bark (CB) -affected and CB -negative LN33 hybrid grapevines. Virus Genes. 41:273 -281. 
 
 
International Plant Protection Convention. 2006. International Standards for Phytosanitary 
Measures (ISPM) 1 Phytosanitary Principles for the Protection of Plants and the Application of 
Phytosanitary Measures in International Trade. Rome, IPPC, FAO pp.1 -8 
 
Martelli, GP. 1993. Rugose wood complex. In Graft -Transmissible Diseases of Grapevines:  
Handbook for Detection and Diagnosis. Food and Agricu lture Organization of the United 
Nations,  Rome pp. 45 –54. 
 
 
Osman, F and A Rowhani. 2008. Real -time RT -PCR (TaqMan) assays for the detection of 
viruses  associated with Rugose wood complex of grapevine. Journal of Virological Methods. Vol 
154(1 -2): 69-75. 
 
Pasacreta, F, Rimerman, T. W et al. 2013. The Economic Impact of the Wine Industry in Canada 
2011.   [http://www.canadianvintners.com/wp -content/uploads/2013/03/Canada -2011 -Wine -
Industry -Economic -Impact -Report -FINAL -3-7-13.pdf ] 
 
Rosa, C, JF Jimenez, P Margar ia and A Rowhani. 2011. Symptomatology and Effects of Viruses  
Associated with Rugose Wood Complex on the Growth of From Different Rootstocks. Am. J. 
Enol.  Vitic. Vol 62:2.  
 
Statistics Canada. 2012. Table 2: Estimate of area, commercial production and farm gate value of 
fruits in Canada, by province, 2011.  
 
 
 
Whattam, M. 2001. Grapevine corky bark disease: a serious quarantine threat of grapevines for  
Australia. Australasian Plant Pathology. Vol 30:379 -380. 
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10.0 Endorsement  
 
 
 
 
_____ ________________________________________  
Chief Plant Health Officer