Xylella fastidiosa found for the first time on pecan (Carya illinoinensis) in Arizona, New Mexico, California and Texas (US)
In the United States, pecan bacterial leaf scorch is a chronic disease associated with Xylella fastidiosa (EPPO A2 List) that can weaken pecan (Carya illinoinensis) and cause major yield losses in susceptible cultivars. In 2015 and 2016, leaf scorch symptoms were observed in pecan plantings in Arizona, New Mexico, California and Texas. Symptoms included tan to light brown necrotic lesions, which often started on the leaf margin and expanded throughout the leaflet, eventually resulting in abscission. Some leaflets exhibited tip necrosis with the end of the leaflet curling upward. Symptomatic and asymptomatic shoots (3 to 4 per tree) were collected from pecan plantings in Arizona, New Mexico, California, Texas and tested (ELISA, PCRs). This study also included samples collected from the USDA-ARS germplasm collection of pecans and hickories which is located in Texas. As a result, 79 pecan trees from Arizona, New Mexico, California and Texas were found to be infected by X. fastidiosa. Although further analysis is required to determine the diversity of X. fastidiosa subspecies in pecan, 2 isolates from Texas could be identified as X. fastidiosa subsp. multiplex. This is the first time that X. fastidiosa is detected in pecan in the Southwestern USA and in the US germplasm collection of Carya species. Finally, it is noted that this finding has implications for international distribution of pecan germplasm, as well as pecan nursery and orchard management in the USA.
Sources
Hilton AE, Jo YK, Cervantes K, Stamler RA, Randall JJ, French JM, Heerema RJ, Goldberg NP, Sherman J, Wang X, Grauke LJ (2017) First report of pecan bacterial leaf scorch caused by Xylella fastidiosa in pecan (Carya illinoinensis) in Arizona, New Mexico, California, and Texas. Plant Disease 101(11), p 1949.