Disease, drought and Weed invasion are plant and Turf killers. But by the time you see them it can be too late. Underhill turfspy early stress detection glasses allow you to see plant and Turf stress 2-10 days before it is visible to the naked eye. You now have a great new weapon against some Old enemies. How does it work? like the technology that makes camouflaged enemies stand out in jungles and forests, our advanced light filtering technology, developed by nasa, turns healthy vegetation dark, exposing plant disease and stress. Why does it work? dying plants signal their distress with changes in how they absorb and reflect sunlight. The earliest signals occur at the outer limits of the human visual spectrum and are rendered invisible compared to the predominant middle wavelengths. Turfspy stress detection glasses filter the overpowering light in the center so that the fringe SPECTRA, which show early plant stress, become visible.