What began as a scientific effort to protect America’s pear orchards has now become one of the country’s most enduring ecological cautionary tales. More than a century after the U.S. Department of Agriculture (USDA) imported Callery pear (Pyrus calleryana) from East Asia, the tree’s descendants have spread beyond orchards and suburban streets, with the species now invading roadsides, abandoned fields and forests across the country. According to the USDA’s National Invasive Species Information Center (NISIC), Callery pear was first imported in 1908 to develop pear trees resistant to fire blight, a bacterial disease that threatened commercial pear production.
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