In the Western United States, spotted knapweed is one of the most widely found nonnative plants. Spotted knapweed was brought to the United States from Eastern Europe in the early 1900s. To control the spread of spotted knapweed, two types of gall flies have been released into areas with spotted knapweed. Unfortunately, these gall flies are not native to the arid grassland ecosystem either. The scientists wanted to study the effect of spotted knapweed and gall flies on the population of deer mic Topics: Active Forest Management, Grasslands, Insects, Wildlife, Deer Mice, Ecosystem, Gall Flies, Grasslands.