The State - News from July 25, 1988

Federal agriculture officials in Contra Costa County will release a breed of fly they hope will stop the spread of yellow star thistle, a dangerous European weed that is taking over rangeland and sickening livestock. Star thistle, which entered the United States in bales of alfalfa, and other feed shipped from Europe, has no natural enemies here and began taking over Northern California ranches, including 470,000 acres in Contra Costa County alone. When horses eat the weed, they grow drowsy, and over time, sick. Enough of the weed can produce death. The U.S. Department of Agriculture will release flies known as Chaetorellia austrials on a Lafayette property where Arabian horses have been growing sick on the weed. The fly has no interest in humans and animals, USDA scientist Charles Turner said, but it is lethal to the yellow star thistle, because its larvae chew up the plant’s seeds.