Longer Exposure Durations Increase Freeze Damage to Turf Bermudagrasses

Abstract

Bermudagrasses, Cynodon sp, are susceptible to winter injury in the transition zone for warm- and cool-season turfgrasses. Our objectives were to determine relative freeze tolerance of recently released and standard cultivars using laboratory-based methodology, and to determine the effect of extended exposure duration on survival. Plants were clonally propagated, then established and acclimated in growth chambers before exposure to a range of temperatures in a freeze chamber. ‘Tifway’ and ‘TifSport’ (−7.9°C) were significantly hardier than ‘Princess’ (−6.9°C), but less freeze tolerant than ‘U-3’ (−8.9°C), ‘Patriot’ (−9.7°C), and ‘Midlawn’ (−10.3°C). Riviera (−8.3°C) was significantly hardier than Princess, but less freeze tolerant than Patriot and Midlawn. In a second set of experiments, acclimated plants were held at constant, subfreezing temperatures for various periods of time in a refrigerated bath. Survival of U-3 and Riviera decreased to 25% or less when exposed to −7.0°C for 2 or 5 d, compared with 100 and 83% survival, respectively, when plants were removed from the bath immediately after equilibrating at −7.0°C. Princess exhibited 89% survival when removed immediately after equilibrating at −5.4°C, but survival after 2, 24, and 72 h was 67, 30, and 11%, respectively. Although minimum exposure temperature is a primary determinant of survival, freeze damage to turf bermudagrasses increased as exposure duration increased.