EFFECTS OF GROUP, CULTIVAR, AND CLIMATE ON THE ESTABLISHMENT AND PERSISTENCE OF XYLELLA FASTIDIOSA INFECTIONS CAUSING ALMOND LEAF SCORCH

• Author(s): Daane, Kent; Kirkpatrick, Bruce; Wistrom, Christina;
• Abstract: Almonds are one of the most widely-grown crops infected by Xylella fastidiosa (Xf). To get a better idea of the conditions that lead to almond leaf scorch outbreaks, and to determine the risks that Xf infections may pose to adjacent vineyards, three factors were assessed that may influence the establishment of Xf infections and almond leaf scorch development: almond cultivar, Xf genetic group, and winter severity. Experimental plots of 100 trees each were planted at two field sites, Armstrong Farm at UC Davis (UCD) and Intermountain Research and Extension Center at Tulelake (IRC). In field plots, equal numbers of highly susceptible Peerless and less-susceptible Butte almond trees were inoculated with grape and two almond Xf isolates. Because Xf infections must survive multiple winters in an almond tree cause almond leaf scorch, field sites were selected with moderate (UCD) and severe (IRC) winter temperatures. To better understand the role of cold temperatures in overwintering Xf infections, a controlled dormancy test was also done. Potted almond trees were inoculated with almond-type Xf, and infected trees held ind dormancy outside, or in cold rooms at 1.7C or 7C. Ten trees from each treatment were brought back into the greenhouse to break bud after 1, 2, or 4 months.
• Publication Date: Nov 2006
• Journal: 2006 Pierce's Disease Research Symposium