In September 2005, the late Dr. Larry Nelson at Clemson University reported preliminary results that doubling clear polyethylene sheets enhances kudzu kill over a single sheet. The photograph shows our doubled clear sheet, which appears to replicate his findings. Perhaps the extra weight moves the sheets closer to the ground, thereby enhancing the "greenhouse effect" and producing higher ground temperatures. The greenhouse effect might also be enhanced because twice the thickness of sheet prevents less infrared light (heat in the form of radiant energy) from escaping from underneath the sheet. October 2005.