Dutch elm disease (DED) has devastated elm populations throughout large portions of the eastern and midwestern United States. This disease has gradually spread westward since its accidental introduction from Europe into North America in 1930. First discovered in California in Sonoma County in August, 1975, DED is a threat to elm populations throughout the state. The California Department of Food and Agriculture is committed to exploring the feasibility of eradicating the disease before it spreads from its initial infection sites.

The invaluable assistance of Paulina Callery in laboratory and field work is gratefully acknowledged. This research was conducted under a cooperative research agreement with the USDA Forest Service, Northeastern Forest Experiment Station work unit NE-2251. The permission of all utility companies in the Owens Valley to place traps on utility poles is gratefully acknowledged. We particularly thank the Los Angeles Department of Water and Power for assistance with tree sampling procedures.