Detection of spores of causal fungi of dieback-type trunk diseases in young, asymptomatic vineyards and mature, symptomatic vineyards

Authors: Fujiyoshi, Phillip; LAWRENCE, DANIEL - University Of California, Davis; TRAVADON, RENAUD - University Of California, Davis; COOPER, MONICA - University Of California - Cooperative Extension Service; VERDEGAAL, PAUL - University Of California - Cooperative Extension Service; SCHWEBS, SETH - Constellation Brands; Baumgartner, Kendra

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2021
Publication Date: 8/22/2021
Citation: Fujiyoshi, P.T., Lawrence, D.P., Travadon, R., Cooper, M., Verdegaal, P., Schwebs, S., Baumgartner, K. 2021. Detection of spores of causal fungi of dieback-type trunk diseases in young, asymptomatic vineyards and mature, symptomatic vineyards. Crop Protection. 150. Article 105798. https://doi.org/10.1016/j.cropro.2021.105798.
DOI: https://doi.org/10.1016/j.cropro.2021.105798

Interpretive Summary: Grapevine trunk diseases threaten grape production worldwide. With no convenient means of eradicating the fungal pathogens, it is critical to prevent the spores from infecting in the first place. However, growers often forego prevention until after symptoms appear, in part because of the lengthy delay between infection and symptom expression. To demonstrate the need for prevention in young vineyards, we compared disease risk for four years in two locations (Napa and San Joaquin) in six young (asymptomatic, < 5-years-old) versus six mature (symptomatic, 13 to 18-years-old) vineyards, all of which were planted with the same wine-grape cultivar, ‘Cabernet-Sauvignon’. Spore traps were used to detect the pathogens with rain during winter, when infections are thought to be most prevalent in California. From 769 spore-trap samples, a combination of culture and DNA-based methods detected 20 species of fungi that cause dieback-type trunk diseases (Botryosphaeria-, Eutypa-, and Phomopsis diebacks), but not those that cause Esca. Rainfall was weakly correlated with detections on a per timepoint basis, but the importance of rainfall on an annual basis was apparent in dry years 1 (12/2013 to 3/2014) and 2 (12/2014 to 3/2015), which had only nine and five detections, respectively. The consistent finding of more detections in mature sites in all four years and both locations, namely of Botryosphaeria-dieback pathogen Diplodia seriata and Phomopsis-dieback pathogen Diaporthe chamaeropis, suggests young vines are at lower risk. Nonetheless, a 50% overlap in species shared between young and mature sites suggests the pathogen community becomes established early on in a vineyard lifespan, thereby emphasizing the need for prevention in young vineyards.

Technical Abstract: Grapevine trunk diseases threaten grape production worldwide. With no convenient eradication method, prevention is critical. However, growers often forego prevention until after symptom onset, in part because of the lengthy delay between infection and symptom expression. To demonstrate the need for prevention in young vineyards, we compared disease risk for four years in two wine-grape crush districts (Napa and San Joaquin) in six young (asymptomatic, < 5-years-old) versus six mature (symptomatic, 13 to 18-years-old) Vitis vinifera ‘Cabernet-Sauvignon’ vineyards. Both active and passive spore traps were used to detect trunk pathogens with rain during the dormant season, when infections are thought to be most prevalent in California. From 769 spore-trap samples, a combination of culture and DNA-based methods qualitatively detected 20 species of fungi that cause dieback-type trunk diseases (Botryosphaeria-, Eutypa-, and Phomopsis diebacks), but not those that cause Esca. Rainfall was weakly correlated with detections on a per timepoint basis, but the importance of rainfall on an annual basis was apparent in dry years 1 (12/2013 to 3/2014) and 2 (12/2014 to 3/2015), which had only nine and five detections, respectively. The consistent finding of more detections in mature sites in all four years and both crush districts, namely of Botryosphaeria-dieback pathogen Diplodia seriata and Phomopsis-dieback pathogen Diaporthe chamaeropis, suggests young vines are at lower risk. Nonetheless, a 50% overlap in species shared between young and mature sites suggests the pathogen community becomes established early on in a vineyard lifespan, thereby emphasizing the need for prevention in young vineyards.