Spruce Budworm Outbreak Near the Prairie–Forest Border in Northwestern Minnesota

Investigators: Susy Svatek Ziegler, Julia Rauchfuss, James H. Speer, Jodi Farrell Sparks, Nathan W. Siegert, Leia Jamieson, Jennifer Passmore, Rhett Johnson

We determined from tree-ring evidence that tree defoliation by spruce budworm began in or before 1998 at Itasca State Park , Minnesota . This was the only outbreak recorded in our tree-ring chronology extending back to 1928. Tree growth before the outbreak was significantly correlated with July Palmer Drought Severity Index.