Hello. In the last week shiny, sticky spots have appeared on the leaves of all the plants in one section of my yard. The plants include Linden trees, hostas, currants, Virginia creeper, maple, and various weeds. It looks like the leaves were sprayed with a squirt bottle full of grease. What could be causing it? Are the spots dangerous for the plants and us there anything I should do about it? Thank you in advance. Ani