Relation between Leaf Fall during Winter in Tankan ‘Tarumizu ichigo’ onto Trifoliate Orange and Climate Conditions

Abstract

In this study, we investigated the rate of brown spotted leaf (BSL) and the rate of leaf fall (LF) in tankan (Citrus tankan Hayata) ‘Tarumizu ichigo’ onto trifoliate orange (Poncirus trifoliata (L.) Raf.) during winter for seven years, and clarified the relation between BSL and LF and the climate conditions. The cumulative rate of BSL and LF in March fluctuated annually in the range of 21.7-99.7% and 5.7-88.3%, respectively. Years with cumulative rate of BSL and LF of 90% or more and 80% or more in March were defined as higher rate years, and years with cumulative rate of BSL and LF of 50% or less and 10% or less were defined as lower rate years. The cumulative rate of BSL and LF in March were related to the average temperature in December. The average temperature in December was 8.5-10.0°C in the higher rate years and 11.5-12.0°C in the lower rate years. The cumulative rate of BSL and LF in March were also related to the precipitation in November. The precipitation in November tended to be lower in the higher rate years than in the lower rate years. In the year when BSL occurred in November, there was little precipitation in November.