Monday, March 1, 2010


The International Fruit Tree Association (#iFruittree) is meeting in Grand Rapids, Michigan, February 27-March 3 for it's Annual Conference. The Conference includes 2 days of speakers and 1 day of orchard tours in the apple production region near Grand Rapids. Here are some take-home messages from selected speakers, and hopefully at least

John Palmer "Apple and Pear Tree Physiology, What Have We Come Up With?"
Key concepts to understand:
Carbon acquisition -- light into total dry matter = linear relationship
• site factors; latitude; cloudiness; frost-free period
• tree factors -- leaf area index; tree height; row orientation; tree width; cultivar
• light interception sets the upper limit for production

Harvest index: total dry matter harvested in fruit (up to 70% possible)
• commercially actually less: why? young trees; biennial; size profile
• management changes have increased harvest index: dwarfing rootstock, minimal pruning, branch manipulation; PGR's
• "We can achieve up to 70% harvest index at maturity"

Fruit quality - think of as "hydrated dry matter ready to eat, attractive, good flavor, saleable, etc."
• shade decreases: fruit weight, red color, SSC, flower bud number, fruit set
• "shady business is to be discouraged in the orchard for more reasons than one"
• never forget link between light and fruit quality

Light interception and distribution; maximize use with minimum misuse: "every bud counts"

Future challenges of "precision horticulture"
• every bud counts
• improved rootstocks
• increased automation
• consistent high fruit quality at POS
• increased development of multidisciplinary teams including molecular biologists
• orchard systems in a wider context -- sustainability and carbon footprint

Steve McCartney "Flower Bud Formation in Apples and Strategies to Help Break Biennial Bearing Habit"
A successful post bloom thinning program in itself not enough to increase return bloom in some varieties
Flower bud initiation: 60-120 DAFB depending on variety (later than I though?)
Use of bio-regulators NAA and ethrel can increase return bloom
Summer NAA: four bi-weekly at 5ppm beginning 8 weeks after bloom
Pre-load (for stop-drop): 5 ppm NAA weekly preceding harvest
Ethrel; single app six weeks after bloom (rate is variety dependent)
What about 5ppm NAA with cover spray every 2 weeks? (Question: simple, but effective?)
More research needed!

Duane Greene "Predicting Thinning, Fruitlet Model"
Greene received the iFruittree 'Researcher of the Year' Award (bio and pict)
Has developed predicting thinning procedure (with colleagues) based on assessing fruit growth rate after chemical thinner application to determine the need for more thinning. Directions available on-line and Excel spreadsheet-based form to run the model.

Terence Robinson "Predicting Fruit Set, Carbohydrate Model"
Basic question: can we predict chemical thinning response using environmental variables?

Factors that affect thinning/final fruit set
• chemical thinner concentration
• application process: uptake, leaf environment, cuticle thickness
• sensitivity of the tree: bloom density, initial set, leaf quality, previous yield history
• temperature, sunlight, tree vigor

Carbon-based hypothesis: fruit sensitivity to chemical thinners primarily a function of carbon supply available for fruit growth from both current production and reserves: temp and sunlight influence trees carbon production; trees more susceptible to chemical thinners when carbon supply is limited and vice-versa

Carbohydrate model
• sunlight + temperature used to calculate photosynthesis = carbohydrate available
• temperature affects carbohydrate demand (higher temperatures more demand via respiration and growth)
• supply vs. demand determines balance (thus, surplus or deficit)

2009 experience:
• Western NY (Lake Ontario): no carbohydrate deficit during thinning window; growers had huge hand-thinning bill; multiple applications necessary to thin Gala
• Eastern NY (Hudson Valley); had some deficit and surplus during thinning window; thinning during deficit worked well

"Optimum thinning level" needs to be developed and visualized as target

Future work needed; test models (relies on good weather forecasts); develop a thinning prediction table; simplify carbohydrate model

Stefano Musacchi "High Density Planting Systems for Apple and Pear"

HDP High Density Planting (HDP, VeryHDP, UltraHDP)

Basis for HDP
• downsize canopy volume and tree height
• pears: quince rootstocks (MC, MH, Adams)
• apples: M.9

• pre-formed nursery tree (knip-boom)
• root cutting
• ridge planting
• Plant Growth Regulators (apogee; auxin and ethephon; GA's; Promalin)

Production always a problem (lower) in the lower canopy

Quality more important than total yield; yield increased only to a point before quality suffers

Latest development: Bibaum apple nursery tree -- dual leader tree developed from double chip bud or bench graft; obviates need for canopy formation; productivity same as single but with less trees; quality equal or improved