October 30 – November 1, 2003

Ventura, CA



Session 1. Water Movement and Stress Management


Chair: Alejandro Barrientos Priego, Universidad Autonoma Chapingo, Mexico

Vice-Chair: Ben Faber, UC Cooperative Extension, Ventura County

The overall goals of the Water Movement and Stress Management Session are to briefly discuss factors which influence the movement of water within the avocado tree and how this in turn affects the tree’s ability to respond to environmental stress.  Brief presentations will be given on the following topics prior to audience discussion.


Alejandro Barrientos – Germplasm variability and water stress

Benjamin Zur – When and how much to irrigate

David Goldhammer – Soil moisture measuring devices

Francisco Mena – Wetted soil volume and how this influences water stress

Robert Heath – The tree’s response to water stress

Ben Faber – How does slope and aspect affect tree water use?



Session 2. Salinity Management


Chair: Stephen Grattan, University of California, Davis

Vice-Chair: James D. Oster, University of California, Riverside


The overall goals of the Salinity Management Session are 1) to present condensed summaries from a variety of experiments that address various aspects of avocado response to salinity, 2) stimulate good discussion among panel members and the audience and 3) answer to the best detail possible the following questions.

a)     Do salinity (osmotic) and specific-ion damage (i.e. chloride and sodium) contribute to avocado’s extreme sensitivity to salinity? If so, which process is more damaging? What influence does reducing the Na/Ca ratio have on tree performance?

b)     Can reclaimed waste-water be used for irrigation of avocado? If so, what are the upper limits for EC, Cl, or Na?

c)     What irrigation management strategies can be adopted in avocado orchards to optimize their response to irrigation with poor quality water?

d)     Is there an integrated approach to salinity management in avocado that can be recommended (i.e. irrigation, amendments, shifting to tolerant rootstocks, etc)?

e)     What is the long-term feasibility of shifting to more salt-tolerant rootstocks?



Stephen Grattan – General overview; Introduction (salinity terms, basic response of trees to salinity)

Salinity tolerance of avocado; the role of the rootstock

Mary Lu Arpaia, Mike Mickelbart – Summary of salinity studies examining various avocado rootstocks

Ricardo Cesped – Response of 'Hass' avocado (Persea americana Mill.) grafted on Mexican and West Indian clonal rootstocks to saline conditions

Nirit Bernstein – Effect of salinity on avocado root and shoot growth

Miriam Zilberstaine The influence of avocado rootstocks on the tree resistance to salinity

Open discussion (Panelists and Audience)

Feasibility of irrigating avocado with reclaimed waste-water; long term salinity studies

Gary Bender – Use of reclaimed water on avocado in San Diego County; problems and solutions

Emi Lahav – The response of avocado to salinity and water-fertilizer management

Joseph Shalhevet – Avocado sensitivity to salinity revisited

Open Discussion (Panelists and Audience)

Irrigation management strategies using saline water

Andreas Neahaus – An integrated approach to irrigation and salinity management

Avraham Meiri – Salinity aspects related to partial soil-surface wetting, Irrigation frequency and leaching timing

Jim Oster – Water, salinity and chloride effects on productivity of Hass avocado

Open discussion (Panelists and Audience)

Concluding Remarks



Session 3.  Quality Management


Chair: Peter Hofman, Department of Primary Industries, Queensland, Australia

Vice-Chair: Allan Woolf, HortResearch, New Zealand


We wish to structure the program by focusing on the following questions: are there avocado quality problems at the marketplace; what the causes are; and what recent advances in research and handling will help us these quality problems. 

We will have 2 presentations that will discuss the US market dynamics for avocado followed by a series of sessions containing short presentations.  Each presentation addressing the stated issue or question will last for no more than 5 minutes.  At the end of each of these presentations there will be time for several questions and open discussion.


The avocado market

Roberta CookChanges in the US marketing of produce, consolidation and globalization

Jan DeLyserWhere avocados fit into this picture

Commercial practices

Jonathan Cutting, Peter Hofman, Reuben Hofshi, Allan Woolf – How to assess quality at the consumer level

Mary Lu Arpaia, Jonathan Cutting, Gawie Eksteen, Peter Hofman – Improving quality to the consumer

Measuring and predicting maturity

Mary Lu Arpaia, Allan Woolf, John Bower – % DM measurement

Mary Lu Arpaia, Reuben Hofshi – Using % DM to predict eating quality

Reducing internal and external damage during cold storage

Peter Hofman, John Bower, Gawie Eksteen, Allan Woolf – Pre-harvest and harvest manipulation

John Bower, Gawie Eksteen – Postharvest treatments

Gawie Eksteen, Jonathan Cutting – What are the NEW future directions for improving outturns

Controlling rots

Kerry Everett, Joseph Smilanick – Reducing inoculum load

Peter Hofman, Kerry Everett, Allan Woolf, Joseph Smilanick – Increasing fruit robustness

Peter Hoffman, Kerry Everett, Jonathan Cutting – How to predict rots severity

Controlling ripening

Peter Hofman, Allan Woolf, Gawie Eksteen – Ethylene

Allan Woolf, Edna Pesis, Julio Retamales – 1-MCP

Summary – Peter Hofman and Allan Woolf



Session 4.  Light Management


Chair: Robert Heath, University of California, Riverside

Vice-Chair: Grant Thorp, HortResearch, New Zealand


The goals of the Light Management Session are to present a broad overview of the science behind light management and the practicalities of implementing theory in the orchard.  The session is designed to stimulate discussion among panel members and the audience and to evaluate the different light management strategies available to growers.


Robert Heath – Introduction

Grant Thorp – Converting sunlight to fruit

Michael Mickelbart and Robert Heath – Photosynthesis, stomatal conductance etc…. what does it all mean?

Grant Thorp – Pruning systems and planting densities

Francisco Gardiazabal (Chile), Reuben Hofshi (California), Grant Thorp (New Zealand) – Making it all work - Commercialization of light and management strategies: Examples and discussion of experiences throughout the world

Bob Heath and Grant Thorp – Conclusions and wrap up



Bonus Session I

Matan Hadari, Bejamin Zur, Guedi Capluto and Liviu Singer (Technion, Israel Institute of Technology) – A three-dimensional model for the light economy of avocado orchards


One of the most important factors in a dense canopy orchard’s productivity and development is the light regime. Subtropical species, such as the avocado tree tend to fill the gaps in the canopy by vigorous growth.  This growth causes shading between the rows, and prevents light from penetrating into the orchard’s canopy during most of the day.

The intercepted radiation over the tree canopy has significant influence over vital processes in tree’s annual cycle, such as pollination, vegetative – reproductive ratios, and fruit yield and quality.  A shaded orchard is typically lower in yield, most of which is located at the tree tops, thus making fruit picking harder, and adding additional costs.

The overall objective of the research presented here is to build and field test a comprehensive model for the light economy of an avocado orchard. The resulting model would be used as a tool for the design of future orchard as well as for the development of optimal pruning practices.

The model uses architectural lighting software, “Radiance”, considered to be the most physically accurate software in the market, coupled with an AutoCAD based models to mimic the light regime in a range of avocado orchard geometries.  Two approaches for evaluating optimal light management are used: Distribution of total light falling on three heights of the outer envelope of the tree, and a “photosynthetically active volume”- the volume of canopy with sufficient light for photosynthetic activity behind above three heights.

Simulation results are presented and compared with light distribution measurements taken under realistic conditions in avocado orchards at kibbutz Regba in northern Israel. The significance of model predictions is discussed.



Bonus Session II

Edgar Quero Gutiérrez (División de Investigación, Instituto Tecnológico, Uruapan, Michoacán, Mexico) – The flow of carbohydrates in the avocado crop (Persea americana Mill. var. Hass) and its anatomic/nutrition relation



Session 5. Pest Management


Chair: Mark Hoddle, University of California, Riverside

Vice-Chair: Joseph Morse, University of California, Riverside


This panel will focus on a discussion of invasive species and their impact on pest management strategies in California.  A series of short presentations will be given introducing this topic and then opened for general discussion.


Mark Hoddle, Joseph Morse – Introduction

Mark Hoddle – New Avocado Pests on the Horizon: Observations from foreign exploration in Mexico  

Jorge Peña – Pests threatening avocado: How can their impact be avoided?

Laurence Mound – Invasive thrips as a threat to Californian avocado production

Manes Wysoki – New invasive pests and present status of some previously introduced ones in avocado plantations in Israel

Pascal Oevering – Glassy Winged Sharpshooters (Homalodisca coagulata) in avocado orchards in southern California



Session 6.  Nutrient Management


Chair: Nigel Wolstenholme, University of Natal, South Africa

Vice-Chair: Guy Witney, California Avocado Commission


This panel will cover the complexity of avocado nutrition, including current techniques used to assess tree nutritional status, nutrient types and application methods and the effects of tree nutritional status on fruit quality. Speakers will provide an introduction to our current understanding of the topic in industries world-wide; and provide the foundation for a discussion on past experiences and future directions in nutrition.


Nigel Wolstenholme – Introduction: Avocado nutrition problems in different parts of the world, and ecophysiological considerations

Guy Witney – Orchard nutrition management approaches

Are there reliable alternatives to standard leaf and soil analysis: fine-tuning leaf and soil analysis

Nigel Wolstenholme – Nitrogen: the key manipulator element

Carol Lovatt – Foliar feeding: How useful is it, and for what elements?

Emi Lahav – Fertigation: pros and cons

Samuel Salazar Garcia – Fertilization for fruit quality

Ben Faber, Guy Witney – Organic avocado orchards

John Menge – Rootstock effects on nutrition management

Nigel Wolstenholme – The importance of mulching

Nigel Wolstenholme – Concluding comments