Forecasting Chilling Accumulation, Rest Completion, and Crop Development in the Southeastern U.S.

1. John G. Bellow Agrometeorologist – Extension Specialist Center for Ocean-Atmospheric Prediction Studies The Florida State University Tallahassee, FL Forecasting Chilling Accumulation, Rest Completion, and Crop Development in the Southeastern U.S.

2. Meetings with stakeholders and advisors indicated a need for additional climate variables emphasizing development and phenology

3. Methods • NWS Coop Data • Data cleaning • Calculation of hourly temp • Calculation of daily, monthly, and seasonal thermal units • ANOVA and Tukey in 293 counties

4. Hourly temperature estimation from: Lat., Long., Max T, Min T • Non-linear fit using FAWN hourly data for 9 sites (3 coastal 6 inland) • Tested on independent FAWN sites: R2 =0.92 (n = 6) ROJAS AND MARTINEZ, 1990

5. Chill units accumulated a 1 CU per hour at optimal temperature and 0.0 CU per hour at Tmax and Tmin The loss of chill units with diurnal warming was not included in the present analysis ANDERSON AND SEELEY , 1992

7. Blueberries • Range of chill required 150 – 800 hrs • Anthesis Feb-Mar; Harvest Apr-Jun • Integration from Oct through Feb. • Role of cool temperatures on floral bud initiation and maturation.

8. CU provide a higher estimation of chilling than chill hours. Chill units estimation Chill hours estimation

9. Chill units estimation Chill hours estimation

10. El Niño signal is an increase in chill Chill units anomalies Chill hours anomalies

11. La Niña brings reduced chilling Chill units anomalies Chill hours anomalies

12. Strawberry • Chill requirements from 700 to 1300 hours • Responses to inadequate chilling include artificial chilling and photoperiod treatments

13. Movement of chill isotherms south in C Fl during El Niño.

14. Increase in chill with El Niño and decrease in chill with La Niña. Signals weak or non-existent in N GA & AL.

15. Peach • Alabama peach growers are facing a serious crisis as a result of the 1998-99 winter weather pattern that has resulted in what may prove to be a record shortage of chilling.  Georgia, South Carolina and Alabama have made application for state labels (24C) for application of Dormex on peaches, nectarines and blueberries to help overcome the shortage of chilling hours being experienced this winter.  It is hoped the Alabama label will be issued by January 21, 1999.  Georgia and South Carolina have already issued their state labels. • Chill requirements 150 – 1050 hours • Anthesis Jan – Feb; Harvest May -July

16. CU methods estimates greater chill accumulation compared with Chill hours using daily mean values.

17. Clear increase in chill for peaches with El Niño

19. Wheat • Winter forage grass • October establishment – Jan – Mar use. • Biomass development and timing are principal concerns.

20. GDD anomalies for wheat consistent with known ENSO signals, El Niño cooler and La Niña warmer. Anomalies broadly significant across tri-state region.

21. Little impact of hourly vs. daily estimation, both appear satisfactory.

22. Subtropicals • 180 to 400 hours of rest • Rest hours for subtropicals reduced during La Niña and increased during El Niño. • Enso anomalies small within S FL • Differences not significant in region

26. Conclusions • Prediction of thermal units for development and phenology based on ENSO climatology seems robust for deciduous fruits and wheat, however results were somewhat weaker for subtropical rest completion. • Signal is consistent with previous knowledge • All forecasts will be enhanced by the integration of ‘season to date’ data. • Weakness from the integration dates range

27. Further directions • Reanalysis for ‘days to completion’ for threshold accumulations for specific cultivars or varietals? • Phenology models for budbreak and anthesis incorporating CU to dormancy and HU to budbreak? • Deployment as probabilistic forecast through agclimate