Since 2004, the gypsy moth has plagued northern Illinois, destroying oak trees in parks and recreation areas. These moths have been migrating slowly from the northern United States to the southern United States. In order to manage the gypsy moth population, the Village of Oak Brook performs aerial sprays in areas where oak trees are present. The treatment consists of a naturally occuring bacterium called Kacillus Thuringiensis (BTK). BTK is highly effective in controlling gypsy moth populations, but is not harmful to people, pets, livestock, or the environment.