Longitudinal Bark Cracking on Trunks of Young Asian Pear Trees in Response to a Rapid Drop in Winter Temperature

Abstract

Freeze-induced longitudinal trunk bark cracking on young Asian pear (Pyrus pyrifolia(Burm.) Nak.) trees was evaluated following a rapid drop in temperature to −21°C in February 1989. Scion cultivars were ‘20th Century,’ ‘Chojuro,’ ‘Hosui,’ ‘Kikusui,’ ‘Niitaka,’ ‘Okusankichi,’ ‘Seigyoku,’ ‘Shinko,’ ‘Shinseiki,’ and ‘Tsu Li’ on Old Home x Farmingdale (OHF) 51, OHF 97, OHF 217, OHF 282, and OHF 333 rootstocks. There was no rootstock effect on bark cracking. The scion cultivar effect was highly significant, however. Cracking of ‘Okusankichi’ trunks (47% of the trees) was significantly greater that ‘Kikusui,’ ‘Shinseiki’ or ‘Tsu-Li‘ which had no cracking. Other cultivars were intermediate between these extremes. Cracked trees were significantly larger in trunk circumference than uncracked trees. Cracked trees had significantly lower trunk circumference relative growth rates during 1989 than uncracked trees. Freeze-induced cracks appeared to be related to the size of the tree within a given scion cultivar.