Investigation into the cause of poor budburst and dying of single spurs in Sauvignon blanc and Cabernet Sauvignon

Project Number
WW 06-43

Project title
Investigation into the cause of poor budburst and dying of single spurs in Sauvignon blanc and Cabernet Sauvignon

Project leader
Halleen, F

Team members
Halleen, F
Mostert, L
Moyo, P
Vermeulen, C
Marais, J
Lesuthu, P
Marais, D

Project description
The aim of the study is to investigate the cause of poor budburst and dying of single spurs in Sauvignon blanc (SB) and Cabernet Sauvignon (CS).
Surveys of affected vineyards were conducted and ten dying spurs were collected from each vineyard to conduct fungal isolations in order to determine if specific trunk disease pathogens are associated with spurs that die. Incidence and severity of spur dieback was determined statistically for both cultivars. Field trials to determine the effect of the time of clean pruning on dieback of spurs, vine vigour and the incidence of trunk disease pathogens that infect wounds and the effect of wound protection during clean pruning were also conducted. Additionally, trials were conducted to determine whether newly discovered Diatrypaceae species (Eutypa-like pathogens) isolated from grapevine and other woody hosts were pathogenic on grapevine. During the 2015 season, shoots in the three vineyards used for the clean pruning trial, were also examined for the presence of the bud mite, Colomerus vitis. Nineteen SB and 17 CS vineyards were surveyed for the presence of dead spurs during April – May 2013 and April – June 2014, respectively. Isolation results show that grapevine trunk disease pathogens could be implicated in the poor budburst and dieback of spurs. Most of the dying spurs collected were observed to be associated with wounds made during clean pruning. Pruning wounds are portals of entry of trunk disease pathogens. The surveys also identified the improper use of wires, plastic clips and elastic bands/tapes/rope, which are used to train young vines into the required shape (i.e. a vertical trunk and two horizontal cordons running alongside a wire) as a significant contributor to dieback. The time of clean pruning and protection of big wounds did not have an effect on the budding and bunch formation of individual SB and CS vineyards. The incidence of trunk disease pathogens remained similar between the treated and untreated wounds for each pruning time in both 2014 and 2015 seasons. Pathogenicity studies conducted with Diatrypaceae species (Eutypa-like pathogens studied), isolated during the grapevine surveys as well as isolates obtained from alternative hosts growing in close proximity to these vineyards, were pathogenic and individually capable of causing brown vascular discolorations when inoculated artificially into grapevine tissues. Examination of buds revealed differences in bud mite infestation among vineyards. High incidences of infestation by the bud mite (>30 % of buds in each treatment), which requires action to be taken, were found in the CS vineyard in Durbanville, followed by the SB vineyard in Constantia and very low infestation in the SB vineyard in Stellenbosch. A number of factors contributed to the dieback phenomenon observed in SB and CS spurs, including grapevine trunk disease pathogens, bud mites, as well as viticultural practices. Environmental factors did not influence the occurrence of dying spurs as similar percentages were observed between the cooler and warmer areas. The time of clean pruning and protection of big wounds did not have an effect on the budding and bunch formation of individual SB and CS vineyards. Treatment of wounds is still highly recommended.

Poster(s)
Moyo, P, Mostert, L, Halleen, F. 2015. Diversity of Diatrypaceae species from grapevines and trees in the vicinity of vineyard in South Africa. Poster presented at the 18th International Plant Protection Congress. 24-27 August. Berlin, Germany.

Presentation(s)
Moyo, P, Mostert, L and Halleen, F. 2013. Investigation into the cause of poor budburst and dying single spurs in Sauvignon blanc and Cabernet Sauvignon. Paper presented at the 35th South African Society for Enology and Viticulture Conference. 13-15 November, Somerset West, South Africa.

Moyo, P, Mostert, L and Halleen, F. 2014. Spur dieback in young Sauvignon blanc and Cabernet Sauvignon vineyards: Results for recent surveys. Paper presented at the 36th South African Society for Enology and Viticulture Conference. 12-14 November, Somerset West, South Africa.

Moyo, P, Mostert, L and Halleen, F. 2014. Diversity of Diatrypaceae associated with grapevines and trees in the vicinity of vineyards in South Africa. Lecture. Friday Forum, 26 June. University of Stellenbosch. Faculty AgriScience. Department of Plant Pathology. Stellenbosch, South Africa.

Moyo, P, Mostert, L, Halleen, F. 2015. Eutypa and its relatives: Pathogens with many hosts. Paper presented at the Institute for Plant Protection in Fruit Crops and Viticulture of the Julius Kühn Institute. 21 August, Geilweilerhof, Germany.

Moyo, P. Mostert, L, Halleen, F. 2016. Diatrypaceae species associated with Eutypa dieback-affected grapevines in South Africa: New insights into an old disease. Paper presented at the 38th South African Society for Enology and Viticulture Congress. 23-25 August. Somerset, South Africa.

Spies, C F J, Moyo, P, Bester, M C, Lesuthu, P, du Plessis, I L, Van Jaarsveld, W.J, Mostert, L, Halleen, F. 2017. Woody plants near vineyards harbour grapevine trunk pathogens. Paper presented at the 50th South African Society of Plant Pathology Congress. 15-19 January, Drakensberg, South Africa.

Moyo, P, Mostert, L, Spies, C F J, Halleen, F. 2017. Diatrypaceae species associated with dieback and cankers of grapevine and other woody hosts in South Africa. Paper presented at the 50th South African Society of Plant Pathology Congress . 15-19 January, Drakensberg, South Africa.

Moyo, P, Mostert, L,South African Society of Plant Pathology Congress Halleen, F. 2017, Characterisation of Diatrypaceae species from grapevine in South Africa. Paper presented at the 10th International Workshop on Grapevine Trunk Diseases. 4-7 July 2017, Reims, France.

Spies, C F J, Moyo, P, Bester, M C, Lesuthu, P, Du Plessis, I L, Van Jaarsveld, W J, Mostert, L, Halleen, F. Diversity and host range of trunk disease pathogens in South Africa. Paper presented at the INRA UMR SAVE. 20 July 2017, Bordeaux, France.

Article
Moyo, P, Mostert, L, Spies, C F J, Damm, U, Halleen, F. 2017. Diversity of Diatrypaceae species associated with dieback of grapevines in South Africa, with the description of Eutypa cremea sp. nov. Plant Diseases, Mnth September v. 102 (1) (p. 220-230)
http://dx.doi.org/10.1094/PDIS-05-17-0738-RE

FinalReport.pdf

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