Encouraging Dormancy with Defoliation and Coordinating Budbreak with Dormant Oil Kitren Glozer,...

Encouraging Dormancy Encouraging Dormancy withwith Defoliation and Defoliation and Coordinating Budbreak with Dormant Oil Coordinating Budbreak with Dormant Oil

Kitren Glozer, Chuck Ingels and Jenny BroomeKitren Glozer, Chuck Ingels and Jenny Broome

Dormancy begins with defoliation and ends with Dormancy begins with defoliation and ends with bud breakbud break

Lack of ‘good chilling’ results in straggly bloom, Lack of ‘good chilling’ results in straggly bloom, weak flower buds and poor leaf outweak flower buds and poor leaf out

Buds don’t develop good vascular connections, Buds don’t develop good vascular connections, so aren’t strong ‘sinks’ for nutrients and PGRsso aren’t strong ‘sinks’ for nutrients and PGRs

Strategy to overcome lack of chilling includes Strategy to overcome lack of chilling includes ‘pushing’ trees into dormancy (chemical ‘pushing’ trees into dormancy (chemical defoliation) and compensating for some of the defoliation) and compensating for some of the chill requirement with dormant oilchill requirement with dormant oil

How to measure chilling?How to measure chilling?

• The Dynamic Model was developed in Israel where there are also warm winter periods

• Unit of chilling = Chill Portion (CP)

• Chill hour model doesn’t adjust for heat cancellation

• Based on four trial years, the broad definition of 850-1500 chill hours as a requirement for ‘Bartlett’ pear should be considered as 56 to 66 chill portions for a minimum to adequate requirement, using the Dynamic Model, forced bloom in mid-winter and full bloom dates

0

10

20

30

40

50

60

70

80

90

100

110

120

1-Sep 1-Oct 31-Oct 30-Nov 30-Dec 29-Jan 28-Feb 30-Mar 29-Apr

CP 04 to 05CP 05 to 06CP 06 to 07CP 07 to 08

0

5

10

15

20

25

30

1-Sep16-Sep

1-Oct16-Oct

31-Oct15-Nov

30-Nov

full bloom 3/21/07

87 chill portions

full bloom 3/18/05

96 chill portions

full bloom 4/25/06109 chill portionsLow heat accum.

full bloom 3/27/08

84 chill portions

When and Why to defoliate?When and Why to defoliate?

Fall defoliation may help to induce early Fall defoliation may help to induce early dormancy dormancy

Inducing early dormancy may help to satisfy Inducing early dormancy may help to satisfy chilling requirementchilling requirement

– Reducing some of the ‘need’ to chillReducing some of the ‘need’ to chill

– Shortening the dormant periodShortening the dormant period Fall urea applications increase cold Fall urea applications increase cold

hardiness in some cropshardiness in some crops

Defoliation treatments in 2006-2007Defoliation treatments in 2006-2007

1% CuEDTA + 2% urea applied 0, 2, 4 CP1% CuEDTA + 2% urea applied 0, 2, 4 CP

Earliest defoliation on 26 Oct, 0 CPEarliest defoliation on 26 Oct, 0 CP

ffruit weight and firmness; no diff. in Brixruit weight and firmness; no diff. in Brix

#1 fruit and estimated total yield #1 fruit and estimated total yield

#2 fruit by approximately 50%#2 fruit by approximately 50%

Defoliation on 3 Nov, 2 CPDefoliation on 3 Nov, 2 CP

– slightly decreased rat tail flowersslightly decreased rat tail flowers

All timings All timings #2 fruit, no #2 fruit, no in #1 yields in #1 yields

Tendency to thin fruit most with earlier defoliationsTendency to thin fruit most with earlier defoliations

Fall Defoliation 2007-2008Fall Defoliation 2007-2008• Chelated Copper + Urea = Fertilizer grade urea (2% v/v) and chelated copper (1% of

Monterey Copper-All; Monterey AgResources • Bartlett/Winter Nellis, planted in 1960 spaced at 12’ x 20’ (182 trees/acre) on the Polder

Ranch Orchard on Russell Road. The soil was Columbia silt loam over Sacto silty clay• CRBD, 3 blocks, 1 acre = 5.5 rows, total trial ~8 acres

x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x
















= Untreated = Defoliant at 3 CP (10-20-07)

= Defoliant at 1 CP (10-11-07) = Defoliant at 7 CP (11-20-07)

Fall Defoliation Results, 2 trial yearsFall Defoliation Results, 2 trial years

• Defoliation treatments in 2006 and 2007 • Slightly delayed primary bloom• thinned primary bloom• improved fruit size and yield (more than doubled %crop

picked at first harvest)• later defoliation more beneficial (3-4 CP in 2006, 7 CP in

2007)• Defoliation in 2007 at 7 CP thinned rat tail bloom

• This may be a tool to • manage harvest timing and reduce the number of picks• reduce cullage• Reduce frost and fireblight risks• No phytotoxicity

Dormant Oil Timing for Control of BloomDormant Oil Timing for Control of Bloom

Timing of dormant oil is usually mid-Dec to Jan 1 for Timing of dormant oil is usually mid-Dec to Jan 1 for convenienceconvenience

This doesn’t account for state of dormancy in the tree and how This doesn’t account for state of dormancy in the tree and how much chilling has accumulatedmuch chilling has accumulated

Polder Ranch, trees planted 1960 and 1970; 10’ x 20’ (218 Polder Ranch, trees planted 1960 and 1970; 10’ x 20’ (218 trees/acre)trees/acre)

Clean Crop Dormant Plus applied in CRBD, 3 reps of 10-12 Clean Crop Dormant Plus applied in CRBD, 3 reps of 10-12 rows each (rows varied from 207 to 408 trees per row)rows each (rows varied from 207 to 408 trees per row)

2007-2008 timings for dormant oil applications: Dec 31 (35 CP), 2007-2008 timings for dormant oil applications: Dec 31 (35 CP), Jan 7 (40 CP), Jan 14 (45 CP)Jan 7 (40 CP), Jan 14 (45 CP)

Collected bloom data (primary bloom, rat tail bloom) and yield Collected bloom data (primary bloom, rat tail bloom) and yield datadata

Trial 2005-2006 Trial 2007-2008Trial 2005-2006 Trial 2007-2008

23 Dec, oil @ 30 CP 23 Dec, oil @ 30 CP #1 & #2 fruit, #1 & #2 fruit, total total yield and yield and Brix (too Brix (too early)early)

Rat tail flowers Rat tail flowers reduced by treatment reduced by treatment at 43 and 54 CP (2 last at 43 and 54 CP (2 last timings)timings)

Yield decreased in the Yield decreased in the first pick with oil at 35 first pick with oil at 35 CP, Dec 31 (too early)CP, Dec 31 (too early)

Yield Yield ↑↑ in the first pick in the first pick with oil at 40 CP, Jan 7with oil at 40 CP, Jan 7

Oil at 45 CP Oil at 45 CP fruit per fruit per tree by 80 to 100 fruit, tree by 80 to 100 fruit, both for #1 and #2 fruitboth for #1 and #2 fruit

Where to get chill data and Where to get chill data and information about calculating chill information about calculating chill

portionsportions Fruit and Nut Center Website (How-to Fruit and Nut Center Website (How-to

Guide on the Dynamic Model and Guide on the Dynamic Model and dataloggers)dataloggers)

Your farm advisor!Your farm advisor!

AcknowledgementsAcknowledgements

Our appreciation to our grower cooperators Our appreciation to our grower cooperators

Joe Green RanchJoe Green Ranch

Greene and Hemley RanchGreene and Hemley Ranch

Van Loben Sels RanchVan Loben Sels Ranch

and to the California Pear Advisory Board and to the California Pear Advisory Board for ongoing supportfor ongoing support

Encouraging Dormancy with Defoliation and Coordinating Budbreak with Dormant Oil Kitren Glozer,...

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