Fireblight, caused by the bacterium Erwinio amylovora, is an erratic and devastating disease of pear orchards. Native to North America, it was first observed in California in the 1890s after slowly crossing the continent from the east, decimating pear orchards in its path. Fireblight has the potential to destroy an established orchard in one season if uncontrolled. With 37,440 acres of hearing trees producing a crop of 353,500 tons valued at $44 million, California pear producers have traditionally spared little in their protection efforts to keep the disease in check.

The authors acknowledge the assistance of: Bruce Bearden, Richard Bethell, Gregory Carnill, David Chaney, James DeTar, Victor Freitas, Chester Hemstreet, Mary Ann Huisman, John Joos, Gordon Morehead, Ross Sanborn, and William Seyman. This project was partially funded by Pear Zone 1, the Extension Service and the Animal and Plant Health Inspection Service of the United States Department of Agriculture.