2017 ASHS Annual Conference

Previous studies have shown that Valencia oranges (Citrus sinensis (Osbeck)), a perennial cultivar requiring 12 to 14 months for fruit maturation, responded to ENSO winter cycles under Florida conditions by developing different levels of soluble solids. A data base for 51 years that included bloom date, yield, preharvest fruit drop and associated weather data for citrus in Florida, USA was developed using USDA-NASS and NOAA data. Bloom date and yield showed small but consistent changes over the 51-year period related to years and specific temperature variables. A citrus flowering monitor expert system that showed good relationships to previous flowering data had parameters with significant differences over a 59-year period. A detailed analysis of several relationships to weather suggest that temperatures have become high enough over this time period to delay initiation of flower bud differentiation (R² = 0.16) but then reduce flower development time by 10 days during the last 20 years compared to the preceding 39 years. Further details about the data set and if climate change is the likely reason for these changes in citrus behavior are discussed.