Managing Larger Crop Loads

Byron Phillips • Valent USA Corporation

January 13 • 14 • 15, 2015

Maximizing Cherry Fruit Size• Fruit Size Determined by:

– Genetic Limitations of Variety– Cell Number– Cell Size

• Cell Number & Size Influenced by:

– Horticultural Practices– Environmental Factors– Hormones (Plant Growth Regulators) & other chemicals

Maximizing Cherry Fruit Size• Strategies

– Training Systems & Pruning Tactics

– Environmental Manipulation

– Bud Size and Strength

– Pollination

– Nutrition

– Plant Growth Regulators

Maximizing Cherry Fruit Size• Training Systems and Pruning Tactics

– Different for Precocious vs. Standard Rootstocks

• Mazzard & Mahaleb– Encourage Precocity & Productivity

• Gisela® and Krymsk™– Reduce Crop Load & Increase Vigor

– Training Systems• Open Vase • Spanish Bush• Steep Leader • KGB• UFO • Central Leader• SSA • Free Standing• TSA • Trellised

Maximizing Cherry Fruit Size

UFO

Maximizing Cherry Fruit Size

OPEN VASE STEEP LEADER

Maximizing Cherry Fruit Size

CENTRAL LEADER

Maximizing Cherry Fruit Size

KGB

Maximizing Cherry Fruit Size• Pruning Strategy and Tactics

– Keep Fruiting Wood Young & Upright

• Remove all pendant & small diameter wood• Remove spurs > 5 years old• Use thinning cuts for light penetration

– Manage sink: source relationships

• Reducing crop load on precocious rootstocks• Increase fruiting wood on standard rootstocks• Manage vigor with optimum leaf area: fruit ratios• Spur-bearers vs. shoot-bearers

Maximizing Cherry Fruit Size• Pruning Timing

– Dormant pruning increases vigor

– Summer pruning (after harvest) moderates vigor

– Summer pruning (before harvest) reduces crop load• May be helpful for disease control, but too late to impact

fruit size

– Prune when weather is dry

– Leave stubs if pseudomonas is present

• Prune when bacteria are quiescent• Consider treating tools with quaternary ammonia

Maximizing Cherry Fruit Size• Pruning Tactics

– Types of Cuts

• Thinning Cuts– Remove pendant wood, weak wood, & improve light

penetration

• Stub Cuts– Branch & spur renewal; new fruiting wood; crop load

management

• Heading Cuts– Stimulate branching, larger leaves (improves leaf area:

fruit ratios)

Maximizing Cherry Fruit Size• Thinning Cuts

Maximizing Cherry Fruit Size• Heading Cuts

Maximizing Cherry Fruit Size• Stub Cuts

Last Year’s Stub Cut

Fruit on shoot below last year’s stub cut

Maximizing Cherry Fruit Size• Stub Cuts

This year’s stub cut (summer

pruned)

These buds will be large

highest quality cherries

next year.

Maximizing Cherry Fruit Size• Leaf Area : Fruit Ratios

– Sink : Source Relationships

• Source: Leaf Photosynthesis• Sinks: Shoot growth, leaf expansion, fruit growth; trunk expansion• Fruit growth includes this year’s crop and next year’s crop

– Optimum Leaf Area : Fruit Ratio = 200 cm2 / fruit

• ~ 5 ½ leaves / fruit• Whole Canopy Basis

– Leaf Area by Type

• Non-bearing spurs• Bearing spurs (2X leaf area of non-bearing spurs)• Shoot Leaves (2X leaf area of bearing spurs)

Maximizing Cherry Fruit Size• Light Penetration

– Training systems & Thinning cuts • Optimize light interception & distribution and photosynthesis

– Shading

• Reduces fruit set

• Reduces fruit size

• Reduces soluble solids

• Delays maturity

• Produces smaller, weaker buds

• Increases weak and dead wood

Maximizing Cherry Fruit Size• Environmental Manipulation

– Stress Reduction

• Cold Injury (winter)

• Frost Protection (spring)

• Drought Stress – Irrigation amounts and critical times

• Covers– Warmer in spring (cell division period)– Cooler in summer (heat stress reduction)

Maximizing Cherry Fruit Size• Environmental Manipulation

– Drought Stress

• Water consumption correlated to canopy and leaf area

• Water loss out of cherry fruit regulated by:

– Water needs of leaves (sink)– Temperature– Humidity

• Critical Periods of Water Needs

– Bloom– Cell Division– Stage III– Post-harvest

Maximizing Cherry Fruit Size• Environmental Manipulation

– Covers

• Increasing use– Rain– Bird exclusion– Temperature moderation & stress reduction

o Warmer temps during spring cell division (Stage I)o Cooler temps during summer heat (Stage III)

Maximizing Cherry Fruit Size• Bud Size & Strength

– Bud size positively correlated to fruit size

• Largest & Strongest Buds:– Adequate water post-harvest– Optimum light penetration– Young spurs / wood– Good nutrient & CHO reserves going into winter

Maximizing Cherry Fruit Size• Pollination

– Earliest flowers produce largest fruit• Bee Placement Timing• ReTain Timing

– Flowers from basal buds on 1-year old shoots

Maximizing Cherry Fruit Size• Nutrition

– Nitrogen• Fall remobilization• Bud size & strength

Maximizing Cherry Fruit Size• Nitrogen & Carbohydrate Source

– Bud Break, Bloom, Spur Leaf & Canopy Development• N from remobilization• CHO from reserves

– Fruit Growth• N from remobilization Stages I & II; Root uptake Stage III• CHO from current season photosynthesis

– Structural growth (shoots, trunk, roots)• N from remobilization first, then root uptake• CHO from current season photosynthesis

– Remobilization of N in the Fall is Critical• Beware defoliation by deliberately induced phytotoxicity• Post-harvest urea applications

Maximizing Cherry Fruit Size• Plant Growth Regulators

– Influence Fruit Size by:

• Increasing Cell Division (Cytokinins)• Increasing Cell Size (Gibberellins)

– ProGibb®

• GA3

• END of pit-hardening phase (Stage II) biggest impact on size– Translucent green vs. straw vs. blush

– Potential Future PGR Strategies• Increase Bud Size• Increase Ovary Size

Thank You