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Physiological effects of pigments and related products

A correspondent wrote:

Hi Dr. Woods-
I seem to recall you doing a post a while back about the physiological effects of pigments and related products .... [I wondered] whether there is any physiological basis to these claims ... [can you] send me the link to your old post (if it exists), or if I am in fact imagining that article whether you'd consider doing a new post about the purported effects of UV blockers.
I didn't do a blog post about it, but I recall sharing a few links on Twitter. My first thoughts on this topic, without reading anything about it, were:
  1. Putting a pigment that makes the grass look greener will make the grass look greener, but what other benefits are there, and are other benefits confused with the color?
  2. Grass is adapted to growth in sun, and grows better in full sun, doesn't it?
  3. I've heard good things from turf managers who have used pigments, but I still go back to point 1.

I've read a bit more about this, and can recommend these articles for those who want to study this a bit more. Here are links, along with a quote from each:

  • Protecting turf from the sun's rays by Danneberger in Golfdom: After asking about many of the things that synthetic pigments may do: "These are just a few of the questions that we don't have a lot of turf science to know. The good news is, research is being conducted across the country to answer these and several other questions."
  • Petrella et al. on The potential photoprotective ability of copper pthalocyanine: Chlorinated copper phthalocyanine (Pigment green 7) was applied to creeping bentgrass.  "High concentrations of green 7 provide photoprotection. Not only do concentrated applications of green 7 increase photochemical efficiency, but data also show a significant increase in total chlorophyll without a shift in chlorophyll a:b. Morphological changes have also been visible; plots treated with higher concentrations of green 7 are physically more dense and produce greater biomass."
  • Is the grass really greener by McCarty et al. in GCM: "After application, these products often provide a temporary visually appealing green color that masks imperfections on the turfgrass surface. In reality, long-term continued application of many of these products may actually have a negative effect on the turfgrass such as increasing surface temperatures and decreasing carbon-dioxide exchange (photosynthetic efficiency).

    The influence of these products on winter hardiness of hybrid bermudagrass putting greens is still under investigation. As photosynthetic properties of bermudagrass (a warmseason [C4] turfgrass) are different from those of bentgrass (a cool-season [C3] turfgrass), we cannot assume pigment-containing products have similar effects on bermudagrass based on results obtained through studies of creeping bentgrass." -- In this experiment, a number of products were used. One of those was TurfScreen, and it was applied at a higher than label rate.

  • Reducing ultraviolet-B radiation affects dollar spot development under field conditions by Benelli et al.: Dollar spot incidence and severity were evaluated on creeping bentgrass to which UV was transmitted (UV+) and to which UV was blocked (UV-). "During both years, the UVB- plots exhibited significantly greater dollar spot incidence and severity on most rating dates compared to the UVB+ plots."

After reading these, and a bit more, it seems there could be something to it. UV light can be bad for grass (a bad thing), and UV light can be bad for dollar spot (a good thing, unless one has blocked the UV light!). It is interesting to follow the ongoing research on this topic, and I'm especially interested to learn more about the effect sizes of measures related to turf performance in the field when managed with pigments or UV blockers, compared to turf managed without.

After evaluating three pigmented products, this was the conclusion of McCarty et al.: "Turfgrasses almost always exhibit certain levels of stress, especially when grown outside of native environments. For now, superintendents are better served by adhering to traditional practices of proper aerification, fertilization and watering of putting greens."


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