Effects of Late‐Season Ethephon Applications on Cold Tolerance Parameters of Four Bermudagrass Cultivars

Abstract

Winter injury of bermudagrass (Cynodon spp.) is a problem across the U.S. transition zone. In an attempt to hasten the onset of autumn senescence and improve cold acclimation, ethephon (3.6 kg a.i. ha−1) was applied three times at 3‐wk intervals beginning on 15 August in 2001 and 2002. Cultivars examined were ‘Riviera’, ‘Midiron’, ‘Princess‐77’, and ‘Tifway’. Tifway exhibited greatest autumn color retention in both years. Ethephon promoted early autumn senescence as indicated by yellowing of the leaves and reduced turfgrass color during ratings in both years. Plant samples removed from plots in autumn and winter were exposed to controlled temperatures to determine those which were lethal to 50% of the material's greenup potential (LT50). Ethephon treatment did not affect freeze tolerance. Freeze tolerance of cultivars differed following seasonal acclimation. The LT50 results were: Midiron < Riviera < Tifway < Princess‐77. In both years greenup results were: Riviera ≥ Midiron > Tifway > Princess‐77. Ethephon treatment slowed greenup in both years. Measurements of proline and linolenic acid levels revealed that Midiron > Riviera > Tifway > Princess‐77. Ethephon treatment did not affect linolenic acid levels; however, it negatively affected proline concentrations in Midiron and Riviera. Since ethephon had little or deleterious effects on bermudagrass cold tolerance, it should not be considered as a strategy to improve winter survival in the transition zone.