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Short-Term Population Dynamics of Erwinia amylovora in Succulent Pear Tissue. Ronald P. Covey, Jr., Assistant Plant Pathologist, Department of Plant Pathology, Washington State University, Tree Fruit Research Center, Wenatchee, Washington 98801; William R. Fischer, Senior Experimental Aide, Department of Plant Pathology, Washington State University, Tree Fruit Research Center, Wenatchee, Washington 98801. Phytopathology 63:844-846. Accepted for publication 10 January 1973. DOI: 10.1094/Phyto-63-844.

Erwinia amylovora was isolated in greater numbers from inoculated apple shoots than from pear shoots when sand was used to facilitate grinding of tissues. Chromatographic grade alumina substituted for the sand increased recovery of E. amylovora from pear shoots but not to the level obtained for apple shoots. When E. amylovora was inoculated into wounded tissue, the frequency of recovery of the pathogen decreased progressively with time after inoculation from 0 to 60 min. Multiplication of the bacteria apparently was negligible up to 24 hr but increased thereafter so that within 32 to 56 hr the number of bacteria approached the concentration in the inoculum. The variation in time required for the bacterial cell number in individual shoots to again reach the concentration of bacteria in the inoculum may account for the variations observed in time for symptom development observed in different shoots.