|FERGUSON, MARY HELEN - Louisiana State University
|CLARK, CHRISTOPHER - Louisiana State University
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2017
Publication Date: 8/15/2017
Citation: Ferguson, M., Clark, C.A., Smith, B.J. 2017. Association of Xylella fastidiosa with Yield Loss and Altered Fruit Quality in a Naturally Infected Rabbiteye Blueberry Orchard. HortScience. 52(8):1073-1079. https://doi.org/10.21273/HORTSCI12044-17.
Interpretive Summary: Diseases caused by the bacterial pathogen, Xylella fastidiosa, are prevalent in the southeastern United States, and in 2004 X. fastidiosa was confirmed as the cause of bacterial leaf scorch of southern highbush blueberries (Vaccinium corymbosum interspecific hybrids) in Georgia and Florida. Bacterial leaf scorch symptoms include marginal leaf necrosis, thin twigs on new growth, leaf drop, stem yellowing, and plant death. Leaf drop combined with yellowed stems is characteristic of blueberry plants with bacterial leaf scorch, and these symptoms help differentiate between this disease and causes of plant decline. Rabbiteye blueberry plant symptoms noted in Louisiana and suspected of being associated with X. fastidiosa included plant death, shoot dieback, marginal necrosis, leaf reddening, and extensive defoliation combined with yellow stems similar to symptoms described on southern highbush blueberry. Rabbiteye blueberry comprises the majority of the ˜3000 acres of blueberry plantings in Louisiana and Mississippi. Objectives of this study were to determine whether there was an association between X. fastidiosa infection and reduced yield and/or fruit quality in rabbiteye blueberry and to what extent X. fastidiosa spread within a rabbiteye orchard. Results suggest that X. fastidiosa infection may cause a substantial decline in yield and berry size of ‘Tifblue’ rabbiteye blueberry plants. Neither P. cinnamomi nor ringspot symptoms were associated with X. fastidiosa infection status. Research and extension workers, as well as growers, should be aware of X. fastidiosa as a potential yield- and survival factor in rabbiteye blueberry.
Technical Abstract: Xylella fastidiosa causes disease in a number of plants in the southeastern United States, including southern highbush blueberry, but little was known concerning its potential impact in rabbiteye blueberry (Vaccinium virgatum). In a naturally infected orchard in Louisiana, mean yields of X. fastidiosa-positive plants were 55% and 62% less than those of X. fastidiosa-negative plants in 2013 and 2014, respectively. Average berry weight was also lower in X. fastidiosa-positive plants. Within three years of testing positive for X. fastidiosa, four of nine X. fastidiosa-positive plants lacked living above-ground growth. However, plants that were X. fastidiosa-negative in 2013 remained so until 2015, suggesting that the bacterium does not spread rapidly in established orchards. Other factors, including soil chemistry variables, Phytophthora cinnamomi, ring nematode, and ringspot symptoms, were also investigated to determine if one of these might predispose plants to infection with X. fastidiosa or be partly responsible for observed yield loss. Researchers, extension workers, and growers should be aware of X. fastidiosa as a potential yield- and survival-impacting factor in rabbiteye blueberry.