Pigments and Paints – Turf Health Promoters Or (Money) Pits?.

Golf courses continue to explore relief options from summer stress on bentgrass [Agrostis stolonifera L. var palustris (Huds.)] putting greens. Colorants and other pigment-containing products have been suggested to relieve such stress by reducing temperatures and respiration, and increasing photosynthesis. However, research supporting these claims are limited thus the objective of this experiment. 

            Four pigment-containing products were selected for two summer field studies: Turf Screen (a combination of zinc oxide and titanium dioxide), PAR and Foursome (copper-based pigments), and a paint designed for use on dormant turfgrass throughout the winter months.  Products were applied weekly for ten weeks.  Two of the products, Turf Screen and PAR, were also used in two 10 day growth chamber studies to evaluate their effects on bentgrass plants under stress from supraoptimal temperatures.

            Higher CO₂ exchange rates for treated turf indicate net photosynthesis is reduced when these products are applied.  Higher evaporation rates for the untreated plots indicate that transpiration is also being affected by these products. Spectroradiometer data showed a significant reduction in the transmission of photosynthetically active radiation when products are applied. None of the tested products lowered canopy temperature, and treated turf plots often exhibited significantly higher temperatures (~1.5°F or 1.0°C) than the untreated controls. Microscopy images indicated Turf Screen (higher viscosity) remained on the leaf surface and covered the stomata while pigments such as PAR (lower viscosity) entered the leaf via stomata. Visual quality, NDVI and WinRHIZO image analysis of turf treated with Turf Screen, PAR, and Foursome was similar to the untreated control in both studies.  

            In summary, these products failed to significantly enhance any plant processes normally associated with improved turf health and quality.  On the contrary, products appeared to disrupt the plant’s ability to cool itself through transpiration. The significant increases in heavy metal concentrations such as zinc and copper should also be considered, especially with long-term use.