Chilling Injury

On warm season turfgrasses chilling injury can occur through the fall. Chilling injury is defined as low temperature stress in the absence of freezing (Levitt, 1980). It readily occurs on warm season grasses growing in the subtropical to tropical regions when temperatures drop below 54 F (12 C) in the fall. Although chilling is most often associated with bermudagrass, it occurs on other warm season turfgrasses.

Besides temperature, light is essential for injury and leaf bleaching to occur (Levitt, 1980; Youngner, 1959). Specifically, Younger (1959) demonstrated the interaction of reduced temperatures and high light intensity. Chilling injury causes several metabolic of physiological dysfunctions to the plant including 1)disruption of the conversion of starch to sugars (amylotytic activity), 2) decreased carbon dioxide exchange, 3)reduction in net photosynthesis, and 4) the destruction/degradation of chlorophyll (DiPaola & Beard, 1992).

Given the range of temperature from freezing (0 C) to 12 C that chilling can occur symptom expression can vary. The most striking symptoms occur, again under high light intensities with rapid temperature drop to -or close to - freezing. Under this scenario symptoms are expressed in 24 to 48 hours. Symptoms appear as bleached out turf often in a camouflage appearance. The bleached out leaves is due to rapid pigment degradation. Although we are not aware of any data or studies, the consensus opinion among researchers in this area is that the serpentine or camouflage pattern occurs because of differential settling of cold air. In other words cold air settles into the lower areas of the turf causing more injury, similar to what occurs in a valley or at the base of a mountain range.

At temperatures in the 8 to 12 C (high 40's low 50's F) chilling injury occurs much slower and is not as drastic. Chilling symptoms appear more uniform and the turf color is a combination of purple, blue, and red shades due to the slow degradation of chlorophyll and the corresponding expression of other pigments and carotenoids.

Control

Preventing chilling injury is nearly impossible if temperatures get cold. If conditions can be predicted prior to occurring covering the turf may help reduce the severity. Applications of gibberellic acid (GA3) within hours of discoloration may help reduce the discoloration (follow labeled directions). Most of these practices work best if the chilling period is of short duration. Painting the turf 'green' is another option if the discoloration is objectionable.

The following are a series of photographs showing various levels of chilling injury with an appropriate description. The first two photographs within the text(above) show the rapid chilling injury that occurred on bermudagrass (Cynodon dactylon) when temperatures drop. The third photograph (to the left) is a close-up of the symptoms.

Photograph credit: (top) Joseph DiPaola, Ph.D., Syngenta Corporation, the 2nd and 3rd picture: Steven Brochu, San Diego Golf Course Superintendents Association (originally posted by Frank Wong, Ph.D, University of California-Riverside.

Chilling injury can occur on multiple warm season turfgrasses. In this case chilling injury occurred on kikuyugrass.

Photograph credit: Larry Stowell, Ph.D. PACE

Chilling injury occurs more indirectly when temperatures are closer to 12 C than 0 C. In this case cool temperatures is causing this bermudagrass fairway to go off color through the slow degradation of chlorophyll resulting in the expression of anthrocyanin pigments and carotoniods.

Photograph credit: Karl Danneberger, Ph.D. The Ohio State University

Discoloration from chilling temperatures in South Florida on 'Champion' bermudagrass green. To the left chilling injury symptoms occurring from cool temperatures, and to the right the symptoms have been masked to some extent by the addition of green paint.

Photograph credit: Mark Hoffer, Bonita Bay Golf Club.

The reddish leaf blade of centipedegrass (Eremochloa aphiuroides)is the result of chilling injury. In this case the turf was exposed to cooling temperatures most likely 10 to 12 C (50 to 54 F) under high light intensity conditions that caused the breakdown of chlorophyll resulting in the expression of red carotenoids and pigments. Notice that the bottom part of the leaf blade (youngest portion) is green. Most likely temperatures increased resulting in turf growth after a brief chilling period. In this case the plant is growing out of the injury.

Photograph credit:Karl Danneberger, Ph.D. The Ohio State University

Light intensity plays an important role in chilling injury. High light intensities are needed for the breakdown of chlorophyll and other plant pigments. This photograph and the bottom photograph show the impact of light. In the photograph to the left notice the red leaf blade (chilling injury). Also, notice that the pen is pointing to a leaf that is laying on the injured leaf blade.

Photograph credit: Karl Danneberger, Ph.D. The Ohio State University

Now in this photograph the leaf has been pulled away from the injured leaf blade. Notice the portion of the leaf blade that was covered is green. The shading effect minimized injury.

Photograph credit: Karl Danneberger, Ph.D. The Ohio State University

References

DiPaola, J.M. and J.B. Beard. 1992. Physiological effects of temperature stress. in (eds. D.V. Waddington, R.N. Carrow, and R.C. Shearman) Turfgrass. ASA Monograph 32. Madison, WI.

Levitt, J. 1980. Responses of plants to environmental stresses. Vol 1. 2nd ed. Academic Press, NY.

Youngner, V.B. 1959. Growth of U-3 bermudagrass under various day and night temperatures and light intensities. Agronomy Journal 51:557-559.

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Authors: Karl Danneberger