In the summer of 1911, squirrels in parts of Alameda County were found to be carrying the bubonic plague virus, the same virus that caused the "black death" plagues in Europe in the Middle Ages. In the previous 10 years, a number of human cases were reported in the Bay Area, including one in Sunol in August 1909.
The federal government, working with Alameda County, started a program of actively killing all wild squirrels to eradicate the disease. Dr. Rupert Blue of the United States Army headed the program and said this about the problem:
“In the last six weeks, plague infected squirrels have been found in Alameda County between Decoto and Lake Chabot, and in Contra Costa County in Wildcat and Pinole canyons. They have also been found in the foothills in Contra Costa County around Lafayette. I have also found such squirrels in the suburbs of Oakland and Berkeley.”
For Decoto, W. E. Pimentel was appointed deputy inspector for the area, overseeing the work of local farmers in poisoning the local squirrels. William A. Boyer was in charge of a work crew of 30 men assisting with the work. Boyer was headquartered on the Nay farm near Decoto.
Over a number of weeks in that summer, over 6,000 acres in Alameda County were put under poison. Reports from the U.S. Public Health Service show that even as late as 1917, there were still a few squirrels found to be carrying the virus.