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Ultraviolet Radiation is Damaging to Turfgrass

Sunlight provides the energy to sustain life on Earth. But while sunlight is needed for healthy turfgrass, too much of good thing can be harmful. Sunlight includes ultraviolet radiation, which can harm turfgrass and most other plants. Ultraviolet radiation (UV) is divided into three different categories based on wavelength, as shown in the following table. The shorter the wavelength the higher the energy, and radiation with higher energy can penetrate further into the cell, causing more damage.

Spectral Region

Wavelength

% of Solar Energy

Comment

UV-A 400-315 nm

6.3

UV-A is the least harmful portion of UV radiation. About 95% of solar UV energy reaching the equator are UV-A. UV-A is responsible for skin tanning and aging.
UV-B 315-280 nm

1.5

About 95% of UV-B is filtered out by ozone in the atmosphere; UV-B, which accounts for 5% of solar UV radiation reaching the Earth, is the portion of UV radiation that is harmful to animals and plants.
UV-C 100- 280 nm

0.5

Although UV-C is the most harmful, it is filtered out by Earth’s stratosphere; essentially no UV-C reaches the Earth’s surface.

Fortunately, the Earth’s air and ozone layer block 97–99% of the Sun’s UV radiation from penetrating through the atmosphere. But during summer heat spells even this relatively small dose of UV can overwhelm turfgrass’ natural protective mechanisms.

Scientists have been studying the effects of ultraviolet-B radiation on plants for decades and have conclusively shown deleterious UV effects such as reduced photosynthesis, biomass reduction, hormone inactivation, decreased proteins, impaired chloroplast function and damage to DNA.  UV-B has greater damaging effects on plants than UV-A because the cell macromolecules such as DNA and protein have strong absorption at 280-320 nm. When UV-B light penetrates DNA the absorbed energy breaks bonds in the DNA strands. Since DNA materials direct building processes that take place within the cell, alterations can result in cell mutations or cells that die off. The effect of UV exposure is similar to physically damaging the plant.

Golf course superintendents have long battled the ill effects of sun and heat stress by using an array of methods such as raising the height of cut, reducing mowing frequency, applying soluble nitrogen and fungicides, syringing. Now, superintendents have another tool for their turf-care toolbox: Turf Screen!

Independent testing has demonstrated that Turf Screen blocks up to 76% of harmful UV-B rays.

Just as sunscreens help prevent sunburn and skin cancer in humans, Turf Screen has been developed specifically for turfgrass. Turf Screen’s UV blockers (titanium dioxide and zinc oxide) form a physical barrier on the turf, reflecting and scattering UV waves and thus preventing the UV radiation from penetrating the cell. Independent testing has demonstrated that Turf Screen blocks up to 76% of harmful UV-B rays.