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Stress Predisposes Young Filbert Trees to Bacterial Blight. L. W. Moore, Assistant Professor, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331; H. B. Lagerstedt(2), and N. Hartmann(3). (2)Research Horticulturist, ARS, USDA, Western Region, Oregon State University, Corvallis 97331; (3)Assistant Professor, Department of Statistics, Oregon State University, Corvallis 97331. Phytopathology 64:1537-1540. Accepted for publication 16 July 1974. DOI: 10.1094/Phyto-64-1537.

The effect of cultural and environmental stress on filbert tree mortality was evaluated in two newly planted orchards. Nonirrigated trees inoculated with Xanthomonas corylina had a high mortality during the second summer after planting. Irrigation significantly reduced mortality of the trees. Tree mortality did not differ significantly between treatments used to prevent sunburn of tree trunks and untreated controls at the Corvallis planting site. However, the use of a reflective paper collar to protect the trunk at Rickreall harmed the trees because sunlight reflected from the surface of this collar injured the trunk and resulted in greater mortality. Summer pruning of trees in the nursery enhanced callusing of the pruning wound of noninoculated trees, but resulted in trees of small diameter. More of the smaller summer-pruned trees died from blight infections after outplanting than did the larger winter-prune nursery trees. Sealing the pruning wound to prevent entry of the pathogen into noninoculated trees also enhanced callusing, but did not influence mortality of noninoculated trees exposed to naturally occurring inoculum. At Rickreall, X. corylina was recovered from discolored and apparently healthy tissues of trees 48 months after inoculation, but none was recovered from tissues of the noninoculated trees that were sampled. In conclusion, the most important factor in reducing mortality of newly established filbert trees infected with X. corylina is adequate irrigation the first 2 to 3 years after planting.

Additional keywords: Irrigation, canker, pruning wounds, sunburn, bacteria in healthy tissue.