Identification, distribution, biology, epidemiology, and control of botryosphaeriaceae species associated with grapevine dieback in California and other grape-growing regions in the United States and Mexico

Botryosphaeria species have recently been identified as important grapevine pathogens worldwide. To date, Botryosphaeria rhodina has been the only species associated with cankers on Vitis vinifera in California. In order to determine the occurrence of other Botryosphaeria species in California, a field survey was conducted of 166 vineyards in 21 counties throughout the state. A total of 1,735 samples of cankered trunks, cordons, and spurs were collected. Botryosphaeria species were the most common fungi isolated from grapevine cankers in California. Morphological identification along with phylogenetic analysis of the internal transcribed spacer region (ITS1-5.8S-ITS2) of the nuclear ribosomal DNA (rDNA) and a partial sequence of the beta-tubulin gene showed that at least seven Botryosphaeria species occur on grapevines in California, including B. rhodina, B. obtusa, B. stevensii, B. dothidea, B. lutea, B. australis and B. parva. Botryosphaeria species were found in grapevine cankers in all grape-growing regions surveyed in California, while incidence and distribution varied with location. Grapevine cankers in California have been mainly associated with Eutypa dieback. However, the frequent recovery of Botryosphaeria from cankers in this study indicates the role of these fungi in grapevine health needs to be more carefully considered.