What makes up a turf pigment

Autumn is a colorful time of the year.  The changing of tree leaves from green to colorful shades of red, purple, orange and yellow cause a dramatic change in landscapes and golf courses.  Due to the change in temperature and day length, leaves slow or stop producing food via photosynthesis. As a result, chlorophyll breaks down, causing the green color to disappear, exposing the range of colors from red to yellow to orange.  The yellow to orange colors come from the pigments carotenes and xanthophyll.

Figure 1.A pigment application being made to a golf course green and approach. Notice the dark green color, which is a result of the pigment.

On golf and athletic fields, pigments, specifically the green pigment, provide color to a turf that is showing stress symptoms or provide a green color to dormant turf.  Some research shows that pigments may contribute to overall turf health. Fungicides with pigments, like Appear^® have been shown to improve turf quality.    How long a pigment lasts depends on environmental conditions and rate of growth, but most last between 20 and 60 days.

Turf pigment products do differ, but also share common properties.  Regarding the green pigment, the synthetic pigment used is a chemical derivative of a phythalocyanine (PC) molecule.   Chlorinated-copper phthalocyanine, or pigment Green 7, is responsible for all of the green pigment products currently in the turf market.

Although Green 7 is the only source of “colorant”, an additional pigment may be added.  Titanium oxide and zinc oxide, which are true pigments, are active ingredients in some pigment products.  Their optical properties (their behavior with visible, ultraviolet and infrared light) are dependent on the size and quality of the particles.  The oxides are known for their high ultraviolet (UV) and photosynthetic active radiation (PAR) reflective capabilities. These properties will decrease as the size of the titanium oxide or zinc oxide particles decrease.

Figure 2.  Pigment product application being made to a semi-dormant turf to make it green. Pigments and dyes are commonly applied to dormant bermudagrass in the southern United States to make them green during the winter

Kaolinite, a clay mineral, is an ingredient added for its optical properties.  On fruit and vegetable crops kaolinite helps prevent sunscald.  Like the oxides, kaolinite is able to reflect solar radiation.  Kaolinite however is required in smaller amounts than the oxides and the particle size is less important.  With some products like Daconil Ultrex^® fungicide, kaolinite is added to the active ingredient.

Besides the type of pigment used, the other aspect that differentiates many products is the deposition aid or sticker.  These additives spread the pigment on the leaf and allow it to last for a longer period under variable weather conditions.  Common deposition aids include silicon emulsions, synthetic latex, resins (plant terpenoids), silicon dioxide, metal oxides, and oils.  Not only do stickers stick, but they also can physically decrease evapotranspiration (ET).  

Several superintendents claim less watering when certain pigment products are applied.  This is not a property of the pigment, but instead a result of the deposition of the sticker, which physically blocks water loss.  In the short term, this could be helpful, but in the end, it could lead to other physiological dysfunctions.