Low Temperature-Kill on NTEP Perennial Ryegrass Under Prolonged Cover of Water and Ice in New England.

Significant winter-kill was observed during 2014 on the 2010 National Turfgrass Evaluation Program (NTEP) perennial ryegrass (Lolium perenne L.) test. Ice cover was present from 6 January until early April 2014. The NTEP perennial ryegrass (PR) test evaluated 88 entries using 3 replicates as a RCB and was maintained at 1.25 cm height of cut. No late fall nitrogen was applied in 2013 while preventative fungicides for low temperature pathogens were applied on 4 December 2013. The ingress of annual bluegrass (Poa annua L.) was observed by the 3rd year of the test (2013) and annual bluegrass (AB) plant counts were made initially on 20 May 2013. During the spring following winter-kill AB plant counts were also recorded on 18 April 2014. Data indicated that AB counts recorded in the spring following winter-kill either increased or did not change from the previous spring, which indicated winter-kill was principally to PR. Initial percent living cover (AB + PR) recorded on 18 April 2014 ranged from 3 to 80% with the balance as dead PR. At the initial rating date of 18 April 2014 tolerant (TOL) PR entries included APR-2036, APR-2320, DLF LGD-3026, PST-2NKM and Rio Vista, which averaged 70% survival. Intolerant (INTOL) PR entries included ISG-30, IS-PR 488, IS-PR 491, PST-204D, and Uno, which averaged less than 10% survival. By the 20 May 2014 rating date the TOL PR entries averaged 85% PR while the INTOL entries averaged only 50% PR. Tolerant PR entries averaged 10% AB and 5% dead PR while INTOL PR entries averaged 23% AB and 27% dead PR. Percent PR was negatively correlated with AB (r=-0.66, n=264) and dead PR (r=-0.40, n=264) at the 20 May 2014 rating date. Forty percent of the initial percent living green cover (AB + PR) recorded on 18 April was accounted for by PR (with AB held constant) while AB accounted for only 5% of the variation (PR held constant). It is suspected that the principal cause of the winter-kill to PR was low-temperature. Median lethal temperatures (LT50) comparing the TOL and INTOL PR entries will be presented.