Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Plants, Soils, and Climate

Department name when degree awarded

Plant Pathology


O. S. Cannon


The purpose of this investigation was to determine the sites of overwintering of Erwinia amylovora (Burrill) Winslow et al . outside of living tissue in Utah. Bacterial isolates were taken from the surfaces of blighted twigs and mummified fruits remaining on the tree; also from internal dead tissue of blighted twigs and mummies, and from soil beneath blighted trees. Each isolate was tested for agglutination with antiserum specific for Erwina amylovora, susceptibility to Erwinia amylovora bacteriophage, production of symptoms in pear seedlings and development of bacterial ooze on green pears.

Both virulent and avirulent isolates were taken from all sites tested. There was also a slight increase in the number of Erwinia amylovora isolates taken as spring approached . There was no apparent difference in apple or pear trees as overwintering hosts.

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