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

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

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

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: R 2 =0.92 (n = 6) ROJAS AND MARTINEZ, 1990

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

Derived forecast products Chilling accumulation BlueberriesChill hoursChill Units T < 7.2 °CT max :15.0 °C; T opt :7.2 °C; T min : -2.5 °C SHINE AND BUCHANAN 1982 StrawberriesT max :20.0 °C; T opt :7.2 °C; T min : 0 °C BIGEY 2002 PeachesT < 7.2 °CT max :14.0 °C; T opt :6.0 °C; T min : -2.0 °C Growing degree daysGDD HourlyGDD Daily Mean EREZ ET AL 1990 WheatT Hour > 0 °CT mean > 0 °C (T-T base ) Rest Completion SubtropicalsRest hours Avocado-1.1 < T < 15.0 °C Mango4.4 < T < 15.0 °C Lychee10 < T < 15.0 °C CRANE AND SHAFFER 2004

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.

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

Chill units estimation Chill hours estimation

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

Chill units anomalies Chill hours anomalies La Niña brings reduced chilling

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

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

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

Peach Alabama peach growers are facing a serious crisis as a result of the 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, Georgia and South Carolina have already issued their state labels. Chill requirements 150 – 1050 hours Anthesis Jan – Feb; Harvest May -July

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

Clear increase in chill for peaches with El Niño

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

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

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

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

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

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