- Author: Ben Faber
Old crop, new crop. What's up there in the trees? Are they big enough to sell? Is there a good set for next year? These are questions every avocado grower has every year, and often all year long. What is up there in the trees is confounded by what is called the "Avocado Illusion".
And boy was I reminded of the issue the other day when harvesting a GEM planting density trial. You don't see GEMs, you feel them, sense them being somewhere near your hand. There's a mass that's different from all the leaves near your hand, and you reach for it with your clipper and by golly you got a live one. But how many have you missed? You really need to search.
In a Science Magazine Letters to the Editor in Dec 1990, Paul Sandorff commented on a book written by Maurice Hershenson called The Moon Illusion. In the book Hershenson described the illusion of why the moon seemed so much larger when it was on the horizon than when it rose to its zenith on the same night. http://science.sciencemag.org/content/250/4988/1646.1
Sandorff said that this illusion applied to avocados since it was so hard to gauge the size of avocados when they were in the tops of the tree canopy. It is the surrounding environment that puts a context to size according to this theory of illusion.
Hershenson added to this observation in the March 1991 Science letters section with the comment that the leaves surrounding the fruit changes our depth perception and so changes our idea of the fruit size.
A further addendum to the avocado illusion theory is that since the fruit are the same color as the leaves (they are both dark green and the fruit unlike most other fruit continues to photosynthesize), it is hard to actually make out the fruit. You can be looking right at the fruit and not see it, confusing it with a leaf.
This illusion makes for difficult fruit estimation. To compensate for this illusion, I will eye the canopy in quadrants, counting the number of fruit, then arbitrarily doubling that total number. It usually gives a pretty close number to the real number of fruit that are in the tree.
By the way, with all the low down fruit in the skirt and with the wet winter, there were a heck of a lot of snails in the canopy dining on fruit.
Photo:
Can you count the number of fruit in this Hass canopy?
Photo: a mess of GEM fruit revealed hiding in the skirt.
- Author: Ben Faber
The meeting will include a presentation by Sam Santander (CDFA-Avocado Inspection Service), Ken Melban (CAC) and a Q/A on avocado growing in the SJV. There will be also 2 visits to GEM growers in the local area. Directions to the tour stops will be provided at the meeting.
San Joaquin Valley Avocado Meeting, December 5, 2022, 8:30 AM to ~12:30 PM
UC Lindcove Research and Extension Center, 22963 Carson Ave, Exeter, CA 93221
PLEASE RSVP to Mary Lu Arpaia, mlarpaia@ucanr.edu with Subject Line: 12/5/22 Avocado Meeting
Mary Lu Arpaia
Professor of Extension, Subtropical Horticulture
University of California
Department of Botany and Plant Sciences
Riverside, CA 92521
- Author: Ben Faber
A recent auction in South Africa was selling 'Maluma' variety of avocado for $92 a tree. That is more than the average price of avocado nursery trees in that country and a lot more than what is paid in California or Florida. That variety has suddenly gotten a huge demand because of its sales characteristics accounting for 13% of the tree sales from one nursery there.
This is a phenomenon that is going on world-wide not just for 'Maluma'. According to a CA nursery producer, the 'Maluma' sale is really a reflection of the world-wide demand for avocado trees and not necessarily this South African variety. Avocado acreage is expanding world-wide. So far 'Maluma' has a US import license, but has not been grown in CA, so we don't know its performance characteristics. That should change soon according to the nurseryman.
Related story: South Africa: Maluma Day to challenge avocado sector's “convenient position”:
http://www.freshfruitportal.com/news/2017/03/08/south-africa-avocado-auction-shows-exorbitant-demand-maluma-trees/
- Author: Jeannette E. Warnert
The GEM avocado is the great-granddaughter of Hass avocado, which is currently the industry standard in California. GEM has all the excellent characteristics of Hass avocados - creamy, nutty flesh; dark, pebbly skin when ripe - and it has additional benefits for the grower, according to Mary Lu Arpaia, a UC Cooperative Extension subtropical horticulturist based at the UC Kearney Agricultural Research and Extension Center in Parlier, Calif.
"Hass avocados are alternate bearing - they will produce a big crop one year, and a small crop the next. GEM is more consistent, so growers can make money every year," Arpaia said. "The trees are also more compact, which means growers have less costs for harvesting and tree maintenance."
GEM was part of an extensive avocado variety breeding program led since the 1950s by UC Riverside plant breeder Bob Bergh. Arpaia took over the program in 1996.
In the early 1980s, Bergh released a variety he called the Gwen. However, Gwen didn't turn black when it ripened, a disadvantage because consumers are accustomed to Hass. In the mid 80s, Bergh planted more than 60,000 avocado variety seedlings on farms across Southern California. GEM, a granddaughter of Gwen, was one.
There are GEM trees growing at the UC South Coast Research and Extension Center in Irvine. Fruit samples are sent to the Kearney Sensory Laboratory, where volunteers judge the fruit's outward appearance and compare the flavor with Hass.
Recently, UC Riverside signed an exclusive license agreement with Westfalia Fruit Estates, a South African company, to market GEM around the world, the university announced. In the United States, the California–based Brokaw Nursery has non-exclusive rights to the GEM avocado.
For information on GEM avocado sensory testing, see the one-minute video below.
- Posted By: Lisa M. Rawleigh
- Written by: Jeannette E. Warnert. Adaptado al español por Leticia Irigoyen.
El aguacate GEM viene siendo el bisnieto del aguacate Hass, la variedad estándar de la industria en California. El aguacate GEM tiene todas las característica excelentes de los aguacates Hass: cremosos, de pulpa almendrada y cáscara oscura y guijarrosa cuando están maduros, y tiene beneficios adicionales para el cultivador, de acuerdo a Mary Lu Arpaia, horticultora subtropical de Extensión Cooperativa de la UC, y quien trabaja en el Centro de Investigación y Extensión Kearney de la UC, ubicado en Parlier, California.
"Los aguacates Hass tienen una producción alternada – producen una cosecha grande un año, y una pequeña al siguiente. El aguacate GEM es más consistente, así que los cultivadores pueden hacer dinero año con año", dijo Arpaia. "Los árboles son también más compactos lo que significa que los cultivadores tienen menos gastos por cosecha o mantenimiento de árboles".
El aguacate GEM fue parte de un programa de cultivo de una extensa variedad de aguacates dirigido desde la década de los 50 por el productor de plantas de UC Riverside, Bob Bergh. Arpaia tomó las riendas del programa en 1996.
A principios de la década de los 80, Bergh dio a conocer una variedad a la que llamó Gwen. Sin embargo, la cáscara de esta variedad no se ponía negra cuando maduraba, una desventaja, ya que los consumidores estaban acostumbrados al Hass. A mediados de la década de los 80, Bergh plantó más de 60,000 variedades de plántulas de aguacates en granjas a lo largo del sur de California. GEM, nieto de Gwen, fue una de esas variedades.
Hay árboles de GEM que crecen en el Centro de Investigación y Extensión South Coast Plaza de la UC en Irvine. De allí se envían muestras del fruto al Laboratorio Sensorial de Kearney, en donde voluntarios califican la apariencia externa de los aguacates y comparan su sabor con la variedad Hass.
Recientemente, UC Riverside firmó un acuerdo de licencia exclusiva con Westfalia Fruit Estates, una compañía de Sudáfrica para comercializar la variedad GEM alrededor del mundo, según dio a conocer la universidad. En los Estados Unidos, el vivero Brokaw, con sede en California, cuenta con los derechos exclusivos del aguacate GEM.