Regional Stone and Pomefruit R&D Forum Tatura 22 October 2014 Managing crop load with Artifical Spur Extinction Dr Sally Bound Senior Research Fellow, Perennial Horticulture Centre, TIA
Background Apple trees produce vast number of flowers Average mature centre leader tree on dwarf rootstock has up to 600 buds with 5 flowers per bud equates to 3,000 flowers per tree desired crop load of 200-250 fruit only want 7-8% of flowers to set Natural abscission too late for fruit size benefits prevention of biennial bearing excessive thinning reduces yield balance fruit number and quality with return bloom
Time of thinning remove excess fruit before fruit cell division complete and total fruit cell numbers determined increase in cell numbers delay in thinning wastes substantial nutrient reserves remove excess fruit early reserves not wasted Mean fruit weight (g) 290 270 250 230 210 190 170 Delay in thinning of 8 weeks results in a 33% loss in fruit weight. 150 0 7 14 21 28 35 42 49 56 Time after full bloom (days)
What is Bud/Spur Extinction? A natural phenomenon observed in some genotypes whereby some buds die off completely and remaining floral buds become reiterative High natural spur extinction corresponds closely to cultivars that are least susceptible to alternate bearing Lauriet al (1995) Genotypic differences in the axillary bud growth and fruiting pattern of apple fruiting branches over several years an approach to regulation of fruit bearing. Scientia Horticulturae 64: 265-281
What is ASE? ASE / ABE = Artificial Spur / Bud Extinction management tool imitating natural bud extinction by reducing bud density through manual removal form of early thinning precisely defines where & how much fruit is set on the tree Aims: -achieve accurate, predictable setting of crop load -promote vigour and performance of floral spurs, - stimulate spur strength, -improve fruit quality, and - ensure regularity of production
Artificial Spur Extinction With spur extinction Unmodified
Floral bud types Spur < 2.5 cm with minimal internode extension Terminal 2.5 cm but 30 cm with internode extension Axillary floral buds on one-year-old shoots
Floral bud types Annual shoot structure: Spring BS = Bourse shoot (developing) BS PS = Primary spur PS
Floral bud types Annual shoot structure: Late summer BS = Bourse shoot (developing) TS = Terminal shoot (last year) TS BS BS
Are all floral buds equal? Terminal buds produced bigger Cripps Pink fruit (2009-2010 season) Primary spur Bourse shoot Fruit Bud type leaf area Specific leaf weight Leaf area Specific leaf weight fresh weight (cm 2 ) (mg.cm -2 ) (cm 2 ) (mg.cm -2 ) (g) Lenswood, SA Spur 21.6 b 7.7 b 143.5 b 7.4 b 129.7 b Terminal 41.4 a 9.1 a 300.4 a 9.1 a 140.3 a Stanthorpe, Qld Spur 7.0 b 9.6 a 153.4 b 9.9 b 152.6 b Terminal 25.4 a 11.1 a 252.2 a 11.5 a 179.3 a Axillary 8.4 b 10.9 a 92.5 c 10.0 b 142.8 c Huon Valley, Tas Spur 18.8 b 9.9 b 197.9 b 9.4 a 158.9 b Terminal 54.9 a 10.8 a 434.0 a 11.0 a 173.1 a Axillary 29.5 b 10.0 b 53.0 c 9.0 b 146.3 c Within a single column and region only, means with a different letter are significantly different.
Are all floral buds equal? Fruit buds are not created equal! Royal Gala and Pink Lady : fruit size largest on terminals next largest on spurs axillaries always produced smallest fruit Larger fruit size on terminals associated with a greater leaf area and/or specific leaf weight of the primary spur and bourse shoot
Natural fruit set responses Proportion (%) of floral buds 70 60 50 40 30 20 10 0 70 60 50 40 30 20 10 0 Tasmania Royal Gala 0 1 2 3 4 5 6 Queensland - Royal Gala S&T FBD = 5 Tot FBD = 6 R/S = M.26 S&T FBD = 7 Tot FBD = 7 R/S = MM.106 0 1 2 3 4 5 6 70 60 50 40 30 20 10 0 70 60 50 40 30 20 10 0 Victoria - Galaxy S&T FBD = 6 Tot FBD = 7 R/S = MM.106 0 1 2 3 4 5 6 Hawke s Bay S&T FBD = 9 Tot FBD = 9 R/S = M.9 0 1 2 3 4 5 6 Number of fruit set per floral bud (spurs & terminals)
Natural fruit set responses Season x Region Proportion (%) of floral buds 70 60 50 40 30 20 10 0 Queensland - Royal Gala Qld2010 Qld2011 S&T FBD = 7; 6 Tot FBD = 7; 16 R/S = MM.106 0 1 2 3 4 5 6 70 60 50 40 30 20 10 0 Victoria - Galaxy Vic2010 Vic2011 S&T FBD = 6; 8 Tot FBD = 7; 13 R/S = MM.106 0 1 2 3 4 5 6 Number of fruit set per floral bud (spurs & terminals)
Fruit set response to ASE Proportion (%) of floral buds 50 40 30 20 10 0 Conv ASE 5 ASE 3 0 1 2 3 4 5 6 Number of fruit set per floral bud (spurs & terminals)
ASE paradigm shift Natural fruit set patterns are affected by cultivar-specific floral behaviour, environment and management Step-wise reductions in FBD using ASE Reduce the proportion of floral buds failing to set Increase the proportion of floral buds setting multiple fruit Precise crop load set by bud extinction Trees respond as if thinned to final crop from fruit set onwards No chemical thinning Conservation of tree carbohydrate resources in early season at a time of scarcity Prediction model of fruit set response each cultivar may need its unique calibration
Benefits of ASE Allows reduction in floral bud density without loss of commercial harvest potential Directs tree carbohydrate resources to only those clusters that will bear fruit for final harvest Eliminates the need for chemical thinning Simplifies hand thinning, as spacing, position and number of clusters are already set
ASE in practice! A= axillary floral buds F= floral buds R= bare area after floral bud removal Note: upright branches tied down
ASE in practice! Tree on left ASE trained to 3 buds/cm 2 TCSA Tree on right unthinned
Implementing ASE Set the tree up by: 1. removing large vigorous branches 2. tying down upright branches
Implementing ASE impose at branch unit level bud numbers set according to the size of the branch (buds/cm 2 branch basal cross-section area) before the onset of growth in early spring floral buds are thinned to the type, position and number required for the target crop load This is not pruning but bud selection and thinning Mafcot disc / Equilifruit disc / Cropulator Notches on disc contain the following information: 1. branch diameter 2. bud (fruit) number (based on 6 buds/fruit per cm 2 BCSA 3. delta (Δ) value
Thanks to PIPS Tree Structure team: New Zealand: Stuart Tustin, Ben van Hooijdonk & Ken Breen (Plant & Food Research) Australia: Dugald Close & Sally Bound (TIA, Perennial Horticulture Centre, University of Tasmania) Simon Middleton, John Wilkie & Heidi Parkes (DEEDI, Applethorpe Research Station, Queensland) Paul James (South Australia) And to all the growers who have given us access to their trees