USING GROWING DEGREE HOURS ACCUMULATED THIRTY DAYS AFTER BLOOM TO HELP GROWERS PREDICT DIFFICULT FRUIT SIZING YEARS

The number of days between peach full bloom date (FBD) and harvest date have been previously related to accumulated growing degree hours during the first 30 days after full bloom (GDH 30). An analysis of historical data (1984–2004) from the California clingstone peach industry indicated that the same early spring temperature data could be used to predict the number of days from FBD to reference date (RD, a date that occurs ten days after pit hardening and is used by the industry to anticipate fruit sizing potential for a given year) and fruit size at reference date (RDFS). In the present study, these data were used to develop a critical value for the response of RD and RDFS to GDH 30. Fruit development rate was substantially increased in years when GDH 30 accumulation values were higher than 6000 compared to when GDH 30 was less than 6000. Under warm spring conditions the trees apparently did not supply resources rapidly enough to support potential fruit growth rates and consequently RDFS was negatively affected.
The combination of the GDH 30 critical value and a web-based decision support tool which calculates GDH 30 values for different weather stations in California allows fruit growers to easily predict difficult fruit sizing years 30 days after FBD.

VIII International Symposium on Modelling in Fruit Research and Orchard Management

G. Lopez, T. DeJong

decision support, fruit development, fruit size, temperature effects, tree modeling

https://doi.org/10.17660/ActaHortic.2008.803.22