First Report of Pecan Bacterial Leaf Scorch Caused by Xylella fastidiosa in Pecan (Carya illinoinensis) in Arizona, New Mexico, California, and Texas

Abstract

Pecan bacterial leaf scorch (PBLS) is a chronic disease that can debilitate pecan and may cause major yield losses in susceptible cultivars. In the 2015 and 2016 growing seasons, symptoms consistent with PBLS (Sanderlin and Heyderich-Alger, 2000) were observed in pecan plantings in AZ, NM, CA and TX. 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. The USDA ARS National Collection of Genetic Resources for Pecans and Hickories (NCGR-Carya) located in Texas, distributes pecan germplasm internationally within constraints outlined by plant import permits of requesting nations. Permits often require source evaluations for PBLS to prevent the spread of the causal agent, Xylella fastidiosa. Samples from NCGR-Carya collections and pecan plantings in AZ, NM, CA, and TX were screened for the presence of X. fastidiosa. S...