As researchers puzzle over the reasons for colony collapse disorder -- the mass death of bees -- German regulators are pointing the finger at pesticides. In May, Germany banned six products made by Bayer, the world pesticide market leader. One prime culprit is a nicotine-like chemical called imidacloprid, an active ingredient in Merit, a Bayer-made insecticide. Merit is widely used in the United States to control lawn grubs, aphids, and other common pests.