Subtropical Fruit Crops Research & Education
University of California
Subtropical Fruit Crops Research & Education

Topics in Subtropics Blog

Which Way World Avocados?

One avocado tree, wholesale, recently sold for $92 in South Africa with 250 trees in a bunch costing about $23,000. They are ‘Maluma', of course, which means it is a new variety that has similar properties to the traditional ‘Hass', and might have some unusual properties like higher productivity, upright growth lending itself to higher planting density and fruit production inside the canopy protecting it from wind and sunburn (Fresh Fruit Portal, 2017).

At a traditional California tree spacing of 273 trees/ha, that would be $25,116 / ha. At some of the new high density spacings of 1 m x 1m, that is nearly a million dollars per hectare alone in trees, let alone the cost of the land and infrastructure. And that is just one hectare, not the multiples of hectares that growers are planting. There are growers investing in five, ten, twenty and more hectares per planting. Big investment.

One million dollars in trees. Nurseries are happy to hear this. If a grower in California or South Africa or Australia wants to plant a new orchard, they are told to get in line. And then, they need to wait for one or two years until the nursery can ramp up supply.   I have gotten calls from China, Philippines, and Italy of all places for trees. Everyone wants to plant trees now, and this has been after a steady increase in world-wide planting that has gone on for the last 20 years. World-wide consumption has seen a steady increase over this time. World-wide, global marketing has assured a steady supply to local markets, regional markets and now all those consumers in far off places like North Dakota in the US, or other countries, such as Beijing and Moscow. French and German consumers have always been reliable importers of the fruit over the years. But now even traditional Italian foodies are eating the fruit.

What is driving this activity? Well, consumers, of course. They have caught the ‘avocado toast' bug. And the health benefits bug. It's all online and a lot of the claims are backed up by science (Scott et al, 2017). According to IndexBox (2017), a data compiling news service, the avocado market expanded at +5.6% per year from 2007 to 2016. Over the last six years, the market displayed a consistent growth; it accelerated sharply from Price of the fruit showed growth. Wholesale prices in 2016 totaled $13,797M, a growth by 23% over the previous year.

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Attached Files
avocado vars

avocado vars
avocado vars

Posted on Thursday, October 4, 2018 at 4:17 PM
Tags: avocado (251), nurseries (3), production (8), sales (3), world (1)

The Thomas Fire and July Heat Wave of 2018

Tree crops growers ranging from citrus to avocado to cherimoya and other exotic fruit tree crops were hit be the fires of December 2018. Many trees were damaged by fire, but many more trees were affected by the heat generated by the fire and to a certain extent the gasses produced by the fire. If the trees were not totally burned, many of the affected trees were growing back from the heat damage. In fact, some avocado trees with completely browned canopies had releafed and flowered in the spring of this year. Flowering was not the norm for damaged trees, but many were recovering.

The outlook for those recovering avocado trees was that they would probably flower in spring of 2019. It is necessary for the tree to grow out a vegetative flush in order for flower buds to form in the late summer. These buds then potentially flower the following spring. The tree most affected by the fires were those along the border of the towns from Goleta to Fillmore. The trees most affected were avocados, partly because they are the most numerous of the subtropical trees grown here, but because they are adjacent to much of the burn area.

On the weekend of July 6-8, extreme temperatures occurred throughout Southern California. These temperatures were in excess of 120 degrees F in some areas. Trees of all species were affected, even native trees, such as coast live oak and sycamore and exotics like eucalyptus and Brazilian pepper. Up to the weekend, temperatures had been very mild. With the onset of the heat, tree stomates were forced to transpire at higher rates than which they could adjust to. Stomata act, to cool a tree, and when water flow through the tree is insufficient, the canopy heats up and turns brown, killing the green tissue. In young trees, the whole canopy may be killed to the ground. In older trees, it is just the green foliage and buds. The same vegetative and floral buds that are damaged in a hot fire, such as occurred in December. The new flush that was happening after the fire was most affected by this second round of heat. Although many different tree species were affected, avocados with their shallow root systems had the least resistance to this rapid transpirational demand.

As leaves wilted from the heat, fruit and branches that had been shaded were exposed to the sun. This resulted in sunburn damage to small and, in some cases, large branches. These damaged branches may sprout in time, but unless they were whitewashed, they may never fully recover.

Fruit suffered both direct and indirect damage from this heat wave. Mature fruit exposed to the heat became very hot and was damaged and unsaleable. Much of that fruit has dropped off the tree. Current season fruit on the trees during this recent heat wave softened and became unmarketable. There also is some evidence that a heat wave like this can cause changes in the composition of the various oils in the avocado, resulting in decreased fruit quality. Many growers had harvestable fruit on their trees at the time of the heat wave, and have lost that crop. Fruit set for the coming season, in many cases, shriveled and has dropped off, as well.

The most devastating aspect of this heat wave was the timing. Most trees were beginning to produce this year's summer flush when the heat hit. This year's summer flush is where the spring 2019 bloom will set to produce the 2020 crop. Thus, the effects of this heat wave will be felt for several years.

For growers, they have suffered fruit losses and now they are faced with cleaning up the trees. They needed to have whitewashed the tree to prevent sunburn. They also need to remove dead leaves and branches, which become a source of inoculum for fungal diseases that can infect good tissue and any fruit that might be in the trees now and in the future.

If trees were thoroughly watered in anticipation of the heat wave, there was less damage, although still extensive. Trees that had been fully hydrated prior to the heat wave were less affected, but did not escape damage. Younger trees under three years of age may have been killed. Older trees will survive, but have lost fruit for at least the crop of 2018 and probably next year's crop. There may not be avocado crop in the affected areas until 2020.

This heat event is unprecedented. There have been hot periods in the past, although none this hot. What made this event so devastating was that the trees did not have time to adjust from a mild period of low evaporative demand to one of high in such a short 24-hour period. Even though this was an extreme event, trees given time to adjust and growers given enough advance warning probably could have sustained less damage with this amount of heat. The rapid occurrence of heat like this would probably be just as devastating in the future.

Photos: heat damaged limbs, trees and fruit

heat damaged tree
heat damaged tree

young heat damaged
young heat damaged

avocado fruit hot
avocado fruit hot

Posted on Tuesday, October 2, 2018 at 5:36 AM

Ag-Field Supervisor Courses in Spanish

Spanish-language Ag Field Supervisor Courses Available at Ventura College

Applications are now being accepted for Ventura College's Agriculture Supervisor Development Program. The 12-week program consists of Spanish-language Level I and Level II courses designed to help potential front-line supervisors develop the skills to effectively lead, communicate and manage field workers while ensuring regulatory standards are met.

The Level I course is for those new to the program; the Level II course is for those who have completed the first course. The courses are designed for Spanish speakers who are learning English. All lessons will be delivered in Spanish and will include weekly English practice. Students are expected to attend all sessions, as well as the graduation celebration where students will receive a certificate of completion.

Applications to the program are now being accepted for the November 1 – February 12 session. Classes meet each Tuesday and Thursday from 9:00 a.m. – 12:00 p.m (Level I) or 2:30 p.m. – 5:30 p.m. (Level II). Courses will be held at Ventura College, Day Road Center, 71 Day Road, Ventura, CA, 93003

Attached Files
learning avocados

learning avocados
learning avocados

Posted on Tuesday, October 2, 2018 at 5:20 AM
Tags: learning (1), school (2), teaching (1)

Asian Citrus Psyllid in Santa Barbara and Citrus Conference

This is a friendly reminder that the Fall ACP Area Wide Management treatment windows for Santa Barbara County are currently under way -- schedule provided below. Please be sure to notify beekeepers in your area before treating, and file your use reports with the county ASAP after finishing to ensure your treatment is acknowledged. 


Thank you to those who have already treated and filed, and those with pending treatments scheduled. The rain forecasted for this week may delay treatments, please just treat when you are able to get back into your orchard. Thank you. 


2018 Fall Treatment Schedule 

Carpinteria, Summerland, Montecito : Sept 16 to Sept 29

Santa Barbara, Goleta, Gaviota, Santa Maria etc : Sept 23 - Oct 6


CITRUS REMOVAL PROGRAM: If you have, or know of, unloved citrus that is not being cared for, the Citrus Matters ACT NOW program through CCM may be able to assist in removing it. Call 1-844-STOP-HLB (1-844-786-7452) for more information, or contact Joel Reyes at or (559) 592-3790. Abandoned or neglected citrus can also be reported to the County Ag Department.


Huanglongbing (HLB) Update

The most recent map and totals for HLB detections are posted at the website . As of September 28 the total number of trees that have tested positive for the HLB bacterium is 874, all in Los Angeles, Orange and Riverside Counties, plus a single ACP from San Bernardino that tested positive. The most recent expansion to the HLB quarantine area is in Tustin, in Orange County.  All HLB detections have been on residential properties and the infected trees have been or are being removed. No HLB has been found in commercial groves to date.


UPCOMING MEETINGS -- Agendas Attached

  • The CPDPC Operations Subcommittee meets Wed., October 3 at 9 am in Visalia. Field cleaning protocols are on the agenda again.
  • The CPDPC Outreach Subcommittee meets Wed., October 3 at 1:30 pm in Visalia.  
  • Regulatory Task Force meets October 12 at 1 pm via webinar. Mitigations for moving bulk fruit across quarantine zones will be reviewed, including field cleaning.
  • All meetings are open to the public and free to attend. Agendas for all program meetings, including webinar information, can be found here, along with minutes from previous meetings:  

Useful Links for Area Wide Management

Summaries of the latest scientific research on combating HLB:


UC recommendations for checking your trees for ACP:


UC-recommended ACP insecticides and treatment protocols, including broad, soft and organic options:


For general updates and information on the state ACP/HLB program and regional activities, go to


ACP Regional Quarantine Information for Santa Barbara County:

To move bulk citrus outside of your quarantine zone (Santa Barbara/Ventura County) you must have a compliance agreement from CDFA and follow the instructions therein. A copy of the compliance information for growers is here:

Contact the County Ag Department/Ag Commissioner's Office (805 681-5600) for more information on the regional quarantine for bulk fruit movement. 

Please keep in mind that the quarantine compliance program for moving bulk fruit is a separate and distinct program and protocol from the Area Wide Management program detailed in this email. Please feel free to contact me with any questions regarding the ACP Area Wide Management program.



Cressida Silvers

ACP/HLB Grower Liaison

Ventura, Santa Barbara and San Luis Obispo Counties

805 284-3310


2018 California Citrus Conference



Attached Files


Posted on Monday, October 1, 2018 at 11:44 AM
Tags: acp (72), adian citrus psyllid (1)

Increasing Avocado Pollinators?

Avocado is a neotropic tree which has been commercialized world-wide, yet it's native pollinators have been little studied. The most frequently studied pollinator has been the old-world insect, Apis mellifera. In commercial orchards it is common practice to introduce honey bee colonies, although it is not clear exactly what the extent of their effect is in California orchards in the presents of native bees and other pollinators. The purpose of this study is to evaluate the range of avocado flower visitors and to assess whether those numbers can be affected by the introduction of gardens that might promote their numbers in the orchards during the avocado bloom period.

Measuring pollinator performance is difficult because of weather impacts, alternate bearing habit and the high level of fruit shedding in avocado. In this study, pollination gardens have been established in three avocado orchards in coastal California near Santa Barbara, just north of Los Angeles. These gardens have been established since 2014 with a variety of perennials that can supply nectar and pollen over the year and especially during the prolonged flower season. The three orchards where the gardens are established each exceed 40 ha. Gardens have been established in just one portion of the orchards, so that flower visitation can be assessed near and far from the gardens. The individual visitation activity of flower visitors was evaluated per unit time and their abundance on avocado flowers near the gardens and away from the gardens. Visitation was also similarly assessed on the pollinator gardens. Pan traps were also used to assess the presence of native bees in the orchards.

The most abundant visitors in all years have been Syrphid spp. along with a variety of other flies and wasps. The most abundant native bee species have included Ceratina, Halictus, Agapostemon and several andrenid species. The highest diversity and abundance of visitors has occurred after the high rainfall year of 2016/17 after previous drought years.

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Attached Files
honeybee at hive

honeybee at hive
honeybee at hive

Posted on Monday, October 1, 2018 at 7:24 AM
Tags: avocado (251), bees (11), crane fly (1), honeybees (6), pollinator (2), syrphid fly (2)

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