Inducing precocity in European Pear 2008 Kitren Glozer Department of Plant Sciences, UC Davis Rachel Elkins UCCE, Lake & Mendocino Counties

Objectives  Reduce the developmental period of young European pear trees to fully cropped condition  Compare rate of reproductive and vegetative development over a 3 year period, with treatments to include single year applications of PGRs, repeated annual applications, and physical means to reduce vegetative vigor (girdling, pruning, limb spreading)

May 7, trees had been planted in Scotts Valley, Lake County 11.2’ x 15’ 6-8 replicate trees/treatment in CRBD

May 7, some treatments were headed to 30” (same timing as grower heading)

May 7, some treatments were headed back to 2-4 good scaffolds

May 19, some treatments were ‘delay- headed’ back to first 2-3 shoot breaks Some trees had very little lateral growth in length or circumference 2 trtments girdled with cable ties – heading timing was May 7 or May 19

Delay heading + Deblading, May 19   All trees that were ‘delay headed’ were also ‘debladed’ (all leaves removed), except for a control ‘delay headed, no deblading ’   Cytokinins = Maxcel (6-BA, Valent), CPPU (synthetic; Prestige, Valent and EUP-CPPU, KIM-C1)   Ethephon   Promalin (GA 4+7, Valent)   Dormex (hydrogen cyanamide; to be applied at early budbreak, 2009) Plant Growth Regulators, May 19

Methods and materials, 2008   Half of PGR-treated reps will be re-treated in Year 2   Year 1: As soon as growth starts in spring, for all treatments except untreated control, deblade terminal leaflets on laterals, tie down or spread laterals to close to horizontal.   PGRs ‘painted’ on laterals or whole tree spray – –MaxCel (500 ppm) – –CPPU (5 ppm) – –MaxCel + CPPU – –ethephon (500 ppm + Regulaid) whole tree spray

Data taken over 3 years Annual growth in length and diameter of laterals per trunk cross-sectional area, number of shoot breaks Precocity = density or canopy filling of bloom, onset of fruiting Number of floral units produced per lateral cross sectional area and length over time (inflorescences) Tree growth = trunk circumference at approximately 10 inches (25 cm) above the bud union, canopy height, canopy spread (2 directions) Yield, yield efficiency = per tree, per trunk cross sectional area, per acre over time

1MaxCel Delayed heading, deblade May 19 2MaxCelHeaded May 7 3CPPU Delayed heading, deblade May 19 4CPPUHeaded May 7 5MaxCel + CPPUHeaded May 7 6Cable ties Delayed heading, deblade May 19 7Cable tiesHeaded May 7 8EthephonHeaded May 7 9Promalin Delayed heading, deblade May 19 10PromalinHeaded May 7 11DormexHeaded May 7 12UTC deblade May 19, no heading 13UTCHeaded May 7 & deblade 14UTC, no debladeHeaded May 7

Best Results, 2008 TRTHeaded May 7 Delayed heading, deblade May 19 3CPPU good increase in vegetative growth, = TCSA and total growth of new shoots (shoot growth/number of new shoot breaks ) 4CPPU improved total growth of new shoots 10Promalin improved total growth of new shoots 12UTC deblade May 19, no heading 13UTCHeaded May 7 & deblade 14UTC, no debladeHeaded May 7

Acknowledgements Our appreciation to our grower-cooperator Andy Scully And the California Pear Advisory Board for ongoing support