Historic and current prevalence of phony peach disease, caused by Xylella fastidiosa, in the United States

Authors: JOHNSON, KENDALL - University Of Georgia; Bock, Clive; BRANNEN, PHILLIP - University Of Georgia

Submitted to: Acta Horticulturae
Publication Type: Proceedings
Publication Acceptance Date: 7/7/2022
Publication Date: 12/12/2022
Citation: Johnson, K.A., Bock, C.H., Brannen, P.M. 2022. Historic and current prevalence of phony peach disease, caused by Xylella fastidiosa, in the United States. Acta Horticulturae. Vol 1352:487-494.

Interpretive Summary: Phony peach disease (PPD) is caused by the bacterium Xylella fastidiosa subspecies multiplex (Xfm), and is a major disease of peach in the southeastern U.S. PPD is characterized by progressive symptoms including shortened branches, darker green foliage, early bloom and most importantly, a reduced fruit size and quality. PPD was first seen in 1885 in Georgia, with major outbreaks in 1915,1929, 1951, and 1976. In intervening years PPD remained prevalent. During the summer of 2020, surveys were performed in peach orchards in Georgia, Alabama, South Carolina, and Florida and additional written surveys were sent to fruit pathologists in 15 other states where the disease was reported historically. Results indicated only 6 states (all in the Southeast) reported the disease since 1970, and in both Georgia and Alabama the disease remains prevalent. There is potential for PPD to spread to other major peach growing regions in the U.S., or internationally. More research is needed to improve our knowledge of PPD to provide improved management of the disease, reduce risk of spread, and reduce impact of Xfm on peach production in the southeastern U.S.

Technical Abstract: Phony peach disease (PPD) is caused by the phytobacterial pathogen Xylella fastidiosa subspecies multiplex (Xfm). Peach (Prunus persica) is an economically important specialty crop in several regions of the world, and PPD is a major disease of peach in the southeastern U.S. PPD is characterized by progressive symptoms including shortened internodes, darker green foliage, early bloom and most importantly, a reduced fruit size and quality. Subsequent to the initial discovery of PPD in 1885 in the state of Georgia, it was not considered important until 1915, when the epidemic had impact on peach production. Further major outbreaks of the disease had detrimental effects on production beyond Georgia in the southeastern U.S. in 1929, 1951, and 1976. In the intervening years PPD remained prevalent in orchards in the region, despite a strict eradication program. In 1959, a map was published showing the distribution of PPD in the southeastern U.S., but no survey has been conducted since to gauge the current prevalence of the disease. During the summer of 2020, surveys were performed in peach orchards in Georgia, Alabama, South Carolina, and Florida and additional written surveys were sent to fruit pathologists in 15 other states where the disease was reported historically. Resulting data indicated 6 states reported the disease since 1970, and in both Georgia and Alabama the disease remains prevalent. Although PPD is restricted to the southeastern U.S., there is the potential for it to spread to other major peach growing regions in the U.S., or internationally. More research is needed to improve our knowledge of pathogen diversity, host range, detection and epidemiology of the strain of Xfm causing PPD. Further fundamental and applied research will contribute to improved management of the disease, reduced risk of spread, and reduced impact of Xfm on peach production in the southeastern U.S.