University of California

Crown gall can spread between walnut trees in nurseries and reduce future yields


Lynn Epstein
Sukhwinder Kaur
James R. McKenna
Joseph A. Grant
William H. Olson
Wilbur O. Reil

Authors Affiliations

L. Epstein is Professor, Department of Plant Pathology, UC Davis; S. Kaur is Staff Research Associate, Department of Plant Pathology, UC Davis; J.R. McKenna was Staff Research Associate, Department of Pomology, UC Davis, and is currently with the USDA Forest Service at Purdue University; J.A. Grant is Farm Advisor, UC Cooperative Extension (UCCE), San Joaquin County; W.H. Olson is Farm Advisor Emeritus, UCCE Butte County; W.O. Reil is Farm Advisor Emeritus, UCCE Yolo County. We thank Susan Bassein for statistical advice.

Publication Information

Hilgardia 62(3):111-115. DOI:10.3733/ca.v062n03p111. June 2008.

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While walnut trees on Juglans hindsiix J. regia ‘Paradox’ rootstocks are highly susceptible to crown gall, it is unknown whether this bacterial disease is acquired in the nursery or the orchard. We selected two groups of gall-free trees in nurseries, those adjacent to trees with and without galls. Two years after being transplanted in the orchard, trees in the group adjacent to those with galls had significantly greater — more than four times more — crown gall incidence than those adjacent to trees without galls (14% versus 3%). In addition, trees in prolonged (17-day), bare-root, unrefrigerated storage before transplanting were associated with higher crown-gall incidence. We also found that crown gall can decrease walnut tree productivity. For every quarter of trunk circumference that was galled, there was a 12% decrease in cumulative nut yield over the first 4 years of production.


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Epstein L, Kaur S, McKenna J, Grant J, Olson W, Reil W. 2008. Crown gall can spread between walnut trees in nurseries and reduce future yields. Hilgardia 62(3):111-115. DOI:10.3733/ca.v062n03p111
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