Project title
Epidemiology and control of spread by grapevine leafroll disease

Project leader
Pietersen, G

Institution
ARC Plant Protection Research Institute

Project description
Identification of viruses associated with leafroll spread in South Africa showed that grapevine leafroll-associated virus type 3 (GLRaV-3) is the dominant virus occurring in all tested plants with leafroll symptoms. A second virus, identified as GVA by IEM, occurred in 23% of GLRaV-3 infected vines. 15% of GLRaV-3 infected vines were also infected with unidentified spherical viruses. Co-infection of GLRaV-3 by GLRaV-1 and GLRaV-2 were detected in two mother blocks. Co-infection of GLRaV-3 by unidentified flexuous rod shaped, virus-like particles was identified in a number of samples. Spatio-temporal data on spread of leafroll was obtained for a second season on 66 mother blocks. Analysis of this data will be done towards the conclusion of the project to ascertain trends. Changes in leafroll disease incidence are presented for these mother-blocks. While the change in incidence in the majority of mother-blocks is below 1%, the total number of leafroll infected vines over all the mother blocks analysed doubled between the two seasons. Analysis of spread of leafroll was done in 8 newly established mother blocks. In one such mother block circumstantial evidence was obtained of leafroll spread from the preceding vineyard. Hyper-spectral analysis of an infected and a healthy Merlot vine showed that significant differences occur between the two at given reflectance wavelengths. Analysis of pixels from aerial images of the block failed to corroborate the hyper-spectral measurement results. Further studies are required to develop a reliable remote sensing technique for leafroll spread. Some indirect evidence for strains of GLRaV-3 were obtained after 6 new PCR systems were developed. However as detection technique anomalies cannot be ruled out, further evidence is required to confirm this. A pilot experiment to assess the usefulness of systemic insecticide treatment to prevent secondary spread of leafroll within rows showed no differences between insecticide treated vines and control vines, but requires the spread data of a second season before conclusions can be made.

Presentation(s)
1. Pietersen, G and Kasdorf, G G F. 2002. Epidemiology of grapevine leafroll disease in South Africa. Winetech Grapevine Virus Workshop, 6 May, Simondium, South Africa.
2. Pietersen, G. 2002. Verspreidingspatrone van rolblaarsiekte in Suid-Afrika. Winetech and VinPro Virus Information Day, 8 May. Worcester.
3. Pietersen, G. 2002. Verspreidingspatrone van rolblaarsiekte in Suid-Afrika. Winetech and VinPro Virus Information Day, 9 May. Paarl.
4. Pietersen, G, Kellerman, U, Oosthuizen, W T and Spreeth, N. 2003. Effect of rouging on natural spread of grapevine leafroll disease in two vineyards in South Africa. 8th International Congress of Plant Pathology, Christchurch, New Zealand.
5. Pietersen, G. 2003. Epidemiology of grapevine leafroll disease in South African vineyards. 27th National Congress of the South African Society for Enology and Viticulture, 5-7 November. Somerset West, South Africa.
6. Pietersen, G. 2003. Epidemiology and control of grapevine leafroll disease in South Africa. 19 August. Constantia.
7. Pietersen, G, Meyer, B and Kasdorf, G G F. Epidemiology of grapevine leafroll disease in South Africa. 2003. Winetech Grapevine Virus Workshop, 5 May. Stellenbosch.
8. Pietersen, G. 2004. Epidemiology of grapevine leafroll virus. Winetech Grapevine Virus Workshop, 11 May. Stellenbosch.
9. Pietersen, G. 2004. Beheer van rolblaarverspreiding in Suid-Afrika. Table and Drying Grape Short Course. 3 August. Upington.
10. Pietersen, G. 2004. Beheer van rolblaarverspreiding in Suid Afrika. Table and Drying Grape Short Course, 10 August. Goudini.
11. Pietersen, G. 2004. Rolblaarvirus navorsing. Winetech and VinPro Information Day, 9 September. Stellenbosch.
12. Pietersen, G. 2005. Spatio-temporal analysis of spread of Grapevine Leafroll virus. Winetech Grapevine Virus Workshop, 10 May. Stellenbosch.
13. Pietersen, G. 2005. Epidemiology and control of grapevine leafroll virus. VinPro Farmers' Day, 11 May, Robertson.
14. Pietersen, G. 2005. Epidemiology and control of grapevine leafroll virus. VinPro Farmers' Day, 11 May, Worcester.
15. Pietersen, G. 2005. Epidemiology and control of grapevine leafroll virus. VinPro Farmers' Day, 12 May, Malmesbury.
16. Pietersen, G. 2005. Epidemiology and control of grapevine leafroll virus. VinPro Farmers' Day. 12 May. Vredendal.
17. Pietersen, G. 2005. Epidemiology and control of grapevine leafroll virus.VinPro Farmers' Day. 22 June. Wellington.
18. Pietersen, G. 2005. Spatial and temporal analysis of spread of grapevine leafroll disease in South Africa. IXth International Plant Virus Epidemiology Symposium, 4-7 April, Lima, Peru.
19. Pietersen, G. 2006. Tackling the grapevine leafroll disease problem in South Africa. 22-25 January. 44th Congress of the South African Society for Plant Pathology. South Africa.
20. Pietersen, G. 2006. Use of remote sensing to monitor the spread of grapevine leafroll disease in South Africa. 3-7 April. 15th Meeting of the International Council for the Study of Virus and virus-like Diseases of the Grapevine (ICVG), Stellenbosch. South Africa.
21. Pietersen, G. 2006. Spatio-temporal distribution dynamics of grapevine leafroll disease in Western Cape vineyards. 3-7 April. 15th Meeting of the International Council for the Study of Virus and virus-like Diseases of the Grapevine (ICVG), Stellenbosch. South Africa.
22. Spreeth, N A, Oosthuizen, W T, Van Rensburg, A, Tooth, D, Rossouw, N and Pietersen G. 2006. Vergelegen, South Africa; a case study of an integrated control strategy to prevent the spread of grapevine leafroll disease. 3-7 April. 15th Meeting of the International Council for the Study of Virus and virus-like Diseases of the Grapevine (ICVG), Stellenbosch. South Africa.

Final report
http://www.sawislibrary.co.za/dbtextimages/FinalReport111.pdf

Pietersen, G. 2004. Die verspreiding van wingerd rolblaarsiekte in Suid-Afrika - 'n moeilike, maar oorkombare probleem. WineLand. Mnth Jun p. 110-113

Article

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