High growing season temperatures limit winter recovery of grapevines from Xylella fastidiosa infection – implications for epidemiology in hot climates

Authors: Burbank, Lindsey; Sisterson, Mark; Wei, Wei; Ortega, Brandon; Luna, Nathaniel; Naegele, Rachel

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2023
Publication Date: 6/6/2023
Citation: Burbank, L.P., Sisterson, M.S., Wei, W., Ortega, B.C., Luna, N.R., Naegele, R.P. 2023. High growing season temperatures limit winter recovery of grapevines from Xylella fastidiosa infection – implications for epidemiology in hot climates. Plant Disease. https://doi.org/10.1094/PDIS-03-23-0492-RE.
DOI: https://doi.org/10.1094/PDIS-03-23-0492-RE

Interpretive Summary: Severity of plant diseases can be affected by climate, and it is important to understand how local conditions contribute to disease outbreaks. Xylella fastidiosa is a bacterial pathogen that causes Pierce's disease in grapevine, mostly in areas with mild winters. In some cases, cold winter conditions allow infected grapevines to recover and grow back disease-free the following year. California's grape growing regions have considerable differences in summer and winter temperatures, and to better understand the impact of regional conditions on disease risk in vineyards, it is important to evaluate how temperature conditions affect disease severity and vine recovery. In this study, winter recovery of three table grape cultivars (Flame, Scarlet Royal, and Thompson seedless) and three wine grape cultivars (Sauvignon Blanc, Cabernet Sauvignon, and Zinfandel) were evaluated under temperature conditions representative of the San Joaquin Valley, an area with hot summers and mild winters that has been severely impacted by Pierce’s disease. Winter recovery was generally limited under these temperature conditions, but with some cultivar variation. Given similar hot summer temperatures of many grape-growing regions worldwide, as well as increasing global temperatures overall, winter recovery of grapevines should not be considered a key factor affecting X. fastidiosa spread and epidemic severity in the majority of cases.

Technical Abstract: Management of widespread plant pathogens is challenging as climatic differences among crop growing regions may alter key aspects of pathogen spread and disease severity. Xylella fastidiosa is a xylem-limited bacterial pathogen that is transmitted by xylem sap feeding insects. Geographic distribution of X. fastidiosa is limited by winter climate and vines infected with X. fastidiosa can recover from infection when held at cold temperatures. California has a long history of research on Pierce’s disease, and significant geographic and climatic diversity among grape-growing regions. This background in combination with experimental disease studies under controlled temperature conditions can inform risk assessment for X. fastidiosa spread and epidemic severity across different regions and under changing climate conditions. California’s grape growing regions have considerable differences in summer and winter climate. In northern and coastal regions, summers are mild and winters cool, conditions favoring winter recovery of infected vines. In contrast, in inland and southern areas summers are hot and winters mild, reducing likelihood of winter recovery. Here, winter recovery of three table grape cultivars (Flame, Scarlet Royal, and Thompson seedless) and three wine grape cultivars (Sauvignon Blanc, Cabernet Sauvignon, and Zinfandel) were evaluated under temperature conditions representative of the San Joaquin Valley, an area with hot summers and mild winters that has been severely impacted by Pierce’s disease, and contains a large portion of California grape production. Mechanically inoculated vines were held in the greenhouse under one of three warming treatments to represent different seasonal inoculation dates prior to being moved into a cold chamber. Winter recovery under all treatments was generally limited, but with some cultivar variation. Given hot summer temperatures of many grape-growing regions worldwide, as well as increasing global temperatures overall, winter recovery of grapevines should not be considered a key factor affecting X. fastidiosa spread and epidemic severity in the majority of cases.