Here invented is method and apparatus for control of ground surface radiative effects. A material is laid out in a field in anticipation of frost or in expectation of crop damage from powdery mildew. The material causes radiative heat loss to the cold night sky due to its low emissivity and it causes ultraviolet-C in natural sunlight to be directed upward to impinge on mildew spores on vegetation where it would be otherwise shaded from the sun.
