Reduction of Xylella fastidiosa Transmission Through Pecan Scion Wood by Hot-Water Treatment.

Pecan (Carya illinoinensis) bacterial leaf scorch disease, caused by the bacterium Xylella fastidiosa, causes leaf loss and reduction in yield of pecans. One of the ways that the pathogen infects newly developing trees is by graft-transmission through infected scion wood. Submersion of pecan scion wood in 46°C water for 30 min greatly reduced transmission of X. fastidiosa following grafting. During a 2-year study with potted rootstock grafted to either hot-water-treated or nontreated scion wood collected from limbs of 'Cape Fear' pecan infected with X. fastidiosa, the pathogen was detected in 21% of the trees that developed from the nontreated scion wood and 0.7% of the trees from the hot-water-treated scions. The hot-water treatment of 46°C for 30 min did not affect graft success. Likewise, scion diameter had no effect on success of grafting or on the efficacy of hot-water treatment. Similar hot-water treatments have been efficacious in elimination of X. fastidiosa and some other pathogens from grapevine cuttings. The use of the hot-water treatment demonstrated in this report could be helpful to individual pecan growers and nurseries that use scion wood that may be infected with X. fastidiosa to reduce the occurrence of pecan bacterial leaf scorch disease in new trees.