blue mold fungus: fungus causing a serious disease in tobacco plants characterized by bluish-grey mildew on undersides of leaves
downy mildew: any of various fungi of the family Peronosporaceae parasitic on e.g. grapes and potatoes and melons
groove: a long narrow furrow cut either by a natural process (such as erosion) or by a tool (as e.g. a groove in a phonograph record)