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

Posts Tagged: avocado

Avocado Aphids?

If you hang around an orchard long enough something unusual will show up, especially when seasons change and there's more rain than usual and it's cold, but not so cold that it freezes and it's prolonged.  So out of San Diego comes a request for an identification of a brown bump on avocado stems.  It's a brown aphid.  Is it something of concern?  Likely not.  Over the years there have been reports of several aphids on avocado.  Check out Walter Ebeling's "Subtropical Fruit Pests" at

These things come and go, and they don't do any damage because once the biocontrol bugs get going, they are fresh meat for them.

avocado aphids
avocado aphids

avocado aphids close
avocado aphids close

Posted on Friday, April 19, 2019 at 5:14 AM
Tags: aphids (3), avocado (272), biocontrol (13)

Controlling Soil pH with a Grass?

This is an intriguing article that popped up about how to improve blueberry production in alkaline soils.  High pH soils are a major issues for many of our tree crops along the coast.  pH is what controls the availability of most plant nutrients and what bacteria and fungi grow in the soil, creating the biosphere.   So can growing a grass cover crop in our orchards improve lemon and avocado production?

A lawn is better than fertilizer growing healthy blueberries

Intercropping with grasses is an effective and sustainable alternative to chemical treatments for maximizing blueberry yield and antioxidant content in limey soils.


Blueberries are prone to iron deficiency - and correcting it increases their health-enhancing antioxidant content, researchers have discovered.

Published in Frontiers in Plant Science, their study shows that growing grasses alongside blueberry plants corrects signs of iron deficiency, with associated improvements in berry quantity and quality. The effects are comparable to those seen following standard chemical treatment - providing a simpler, safer, cheaper and more sustainable strategy for blueberry farming on sub-optimal soils.

What do superfruits eat?

All soils are rich in iron, but nearly all of it is insoluble.

"Most plants get enough iron by secreting chemicals that make it more soluble," explains senior study author Dr José Covarrubias, Assistant Professor of Agriculture Sciences at the University of Chile. "These iron 'chelators' can be released directly from the roots, or from microbes that grow among them, and allow the iron to be absorbed."

"Blueberries, however, lack these adaptations because they evolved in uncommonly wet, acid conditions which dissolve the iron for them."

As a result, most of the world's relatively dry or alkaline ('limey') cropland is unsuitable for optimal blueberry growth.

"Iron is essential for the formation and function of plant molecules like chlorophyll that allow them to use energy," Covarrubias continues. "That's why iron deficiency shows up as yellowing leaves - and drastically reduces plant growth and yield.

"And in blueberries, iron-dependent enzymes also produce the 'superfruit' antioxidants responsible for their celebrated blue skin and health-enhancing effects."

Strong blueberries must pump iron - but at what cost?

There are two approaches to correcting iron deficiency in blueberries: acidify the soil, or add synthetic iron chelators. Each has its drawbacks, says Covarrubias.

"The commonest industrial approach is soil acidification using sulfur, which is gradually converted by soil bacteria into sulfuric acid. The effects are slow and difficult to adjust - and in waterlogged soils, hydrogen sulfide might accumulate and inhibit root growth.

"Acids can also be added directly via irrigation systems for more rapid acidification - but these are hazardous to farmers, kill beneficial soil microbes, and generate carbon dioxide emissions.

"A commoner strategy among growers is application of iron bound to synthetic chelators - often sold as 'ericaceous fertilizer' - but these are very expensive and leach potentially toxic chemicals into the water table."

A cheaper, safer alternative is needed for efficient large-scale blueberry production. Thankfully, one already exists.

"Grasses - which are well-adapted to poor soils - can provide a sustainable, natural source of iron chelators via their roots when grown alongside fruiting plants. Intercropping with grass species has been shown to improve plant growth and fruit yield in olives, grapes, citrus varieties - and most recently, in blueberries."

A grassroots approach to sustainable blueberry farming

Now, Covarrubias and colleagues have brought intercropping a step closer to the mainstream of blueberry cultivation.

For the first time, they measured the effects of different methods of iron chelation on antioxidant content and other fruit qualities in blueberries.

"In an orchard of 'Emerald' blueberry bushes cultivated in alkaline (pH 8) soil, we compared the effects of five different iron chelation treatments: a 'gold-standard' synthetic iron chelator (Fe-EDDHA), intercropping with grass (common meadow grass or red fescue), cow's blood (Fe-heme), or no treatment (control)."

"We found the association with grasses increased not only the total weight and number of blueberries per plant, but also the concentration of anthocyanins and other antioxidant compounds in their skins, compared to control. The effect sizes were comparable with the proven synthetic chelator Fe-EDDHA, whereas applications of Fe-heme from cow's blood - a fertilizer commonly used in home gardens - had no significant effect."

The beneficial effects paralleled improvement in the plants' iron status (leaf color), which was also comparable between the grass-associated and the Fe-EDDHA-treated plants. None of the treatments had a significant effect on average berry weight

Turf is ready to roll out for healthier blueberries

A potential limitation of intercropping observed in the study was a decrease in berry firmness, since firmer berries are favored by consumers.

"The association with grasses decreased berry firmness compared with control plants, whereas the berries collected from plants treated with Fe-EDDHA reached intermediate values.

"However chemical analysis showed a non-significant trend towards increased ripeness in the berries collected from the intercropped plants, which could account for this small difference."

Intercropped plants also required an additional water supply to maintain a similar soil moisture to other treatments, but plant management was otherwise straightforward and the same across groups. The grasses were kept cropped between 5 and 15cm - a typical range for an attractive mown lawn.

"Our findings validate intercropping with grasses as a simple, effective, sustainable alternative to standard iron correction strategies in blueberries," concludes Covarrubias. "Both commercial and private growers can put this strategy to use right away to boost their blueberry crop and antioxidant content."


Please link to the original research article in your reporting:

Frontiers is an award-winning Open Science platform and leading Open Access scholarly publisher. Our mission is to make research results openly available to the world, thereby accelerating scientific and technological innovation, societal progress and economic growth. We empower scientists with innovative Open Science solutions that radically improve how science is published, evaluated and disseminated to researchers, innovators and the public. Access to research results and data is open, free and customized through Internet Technology, thereby enabling rapid solutions to the critical challenges we face as humanity. For more information, visit and follow @FrontiersIn on Twitter.

soil colors
soil colors

Posted on Tuesday, April 2, 2019 at 11:17 AM
Tags: acid (2), alkaline (2), avocado (272), citrus (304), nutrients (20), pH (6), soil (22)

Avocado and Laurel Wilt Webinar and CEUs

Next up on Ag Experts Talking is Laurel Wilt Disease which is causing major damage in the native tree populations of the south east United States and the avocado groves in particular.  Learn what is being done there and what the potential threat is to California avocados.

What Are the UC Ag Experts Talking About?

What is involved in the webinars?

A series of 1 hour webinars, designed for growers and Pest Control Advisors, will highlight various pest management and horticultural topics for citrus and avocados.  During each session, a UC Expert on the subject will make a presentation and entertain write-in questions via chat during and/or after the presentation. As we develop this program, we may expand to other crops.  

Topics: pests and diseases of citrus, avocado and other crops

What are the topics and how do I register?

Laurel Wilt (March 20, 2019 from 3-4 pm)

Dr. Monique J. Rivera will present current knowledge of the laurel wilt, the biology and ecology of its vector - Ambrosia beetles, current known location of the disease in the US, Identifying the disease, and the laurel wilt disease prevention in California.Dr. Monique J. Rivera will present current knowledge of the laurel wilt, its biology and spreading. One DPR CE unit (other) and one CCA CE unit (IPM) are pending.



Management of Glyphosate-Resistant Weeds in Orchard Crops (April 24, 2019 from 3-4pm)

Dr. Brad Hanson, cooperative extension specialist, will discuss what is herbicide resistance, current state of resistant weeds in CA permanent crops, identification and lifecycle of key glyphosate-resistant weeds, selection pressure for resistant biotypes and species, herbicide modes of action, and examples of herbicide programs for orchard crops. One DPR CE unit (other) and one CCA CE unit (IPM) are pending.



Are there Continuing Education units?

When the subject discusses pest or disease management, continuing education units will be requested from DPR (1 unit per session).  Participants will pre-register, participate in the webinar and be awarded the unit.  The sessions will be recorded and hosted on this web site for future study.  However, continuing education units will be awarded only to the participants who attend the live version of the webinar.  

Who is involved?

This webinar series is brought to you by Ben Faber (UC ANR Ventura Advisor) and Dr. Beth Grafton-Cardwell (Depart of Entomology UC Riverside Extension Specialist) with the technical support of Petr Kosina (UC IPM Contect Development Supervisor) and Cheryl Reynolds (UC IPM Interactive Learning Developer). 


laurel wilt stages (2)
laurel wilt stages (2)

Posted on Friday, March 8, 2019 at 6:35 AM

What’s Up with my Avocado Tree?

So a question comes in about a problem with a backyard avocado tree.  And it would seem the first question would be about the overgrowth happening at the base of the trunk.  This a ‘Fuerte' avocado that is grafted on a seedling avocado rootstock.  It's not unusual to see an overgrowth, but this is the most extreme example I have ever seen.  So it's basically an incompatibility between the graft and the rootstock.  In many cases this is no big problem and trees can live a long time, as this tree has.

But the homeowner wasn't asking about the unusual growth at the base, but the canker that had appeared in the center of the trunk near the base.

This has the classic white sugar exudate that occurs with a wound of any kind in avocado.  The sugary sap that contains the unusual mannoheptulose 7-carbon sugar characteristic of the laurel family to which avocado belongs will ooze out of the wound and result in a white crust (Read more about this sugar at: ).

Anyway, so this backyard tree is in an area that is getting 10 minutes of lawn watering a day.  Lawns and avocados don't get along.  And avocados don't get along with short, shallow irrigation that result in salt accumulating in the root zone. Which is what has happened here.  Salt stress and the result is an infection of bacterial canker ( ).  

It's not fatal in an old tree like this, but it can predispose the tree to root rot. And that's not something that is easy to treat in backyard settings.

Posted on Monday, March 4, 2019 at 5:56 AM
Tags: avocado (272), bacterial canker (2), stress (10), water (47)

Avocado Disease on High

UAV-based Remote Sensing Can Help

      Avocado Growers by

                Detecting Asymptomatic Pathogen

And maybe a lot of other problems like Shot Hole Borer-Fusarium Dieback in Avocado and other California tree species and maybe Huanglongbing in citrus.

GAINESVILLE, Fla. — Remote imaging can effectively detect a pathogen that endangers the $100 million-a-year Florida avocado industry – even before the trees show symptoms — University of Florida scientists say.

Yiannis Ampatzidis, an assistant professor of agricultural and biological engineering at the UF Institute of Food and Agricultural Sciences, led recently published research that shows that multispectral cameras can detect laurel wilt on avocado trees. The approach costs less than manually trying to detect the laurel wilt pathogen, Ampatzidis said, though UF/IFAS researchers don't know yet the cost differential.

Avocados provide an estimated $100 million-a-year economic benefit to the state's economy, according to UF/IFAS research. California grows most of the nation's avocados, but Florida is the second-leading producer. About 95 percent of Florida' avocados are grown in South Florida, particularly in Miami-Dade County. So UF/IFAS researchers first infected avocado trees with laurel wilt at the UF/IFAS Tropical Research and Education Center in Homestead, Florida.

Then they brought those trees to the UF/IFAS Citrus Research and Education Center in Lake Alfred, Florida, where Jaafar Abdulridha, a postdoctoral researcher for Ampatzidis, tested if the remote-sensing techniques would discern the laurel wilt pathogen. At the Citrus REC, UF/IFAS researchers identified wavelengths that they can use to detect laurel wilt early in avocados.

Multispectral cameras can capture data within specific wavelengths across the electromagnetic spectrum, said Ampatzidis, who specializes in precision agriculture. Humans can only see very small areas of the spectrum.

“In general, growers need to scout their field and visually detect infected plants,” said Ampatzidis, a faculty member at the UF/IFAS Southwest Florida Research and Education Center in Immokalee, Florida. “It is very time-consuming, labor-intensive and costly. And of course, they can only detect diseases based on their symptoms.”

“Using different filters, we can separate wavelengths,” he said. “So, these multispectral cameras are sensitive to particular wavelengths.”

The proposed system could detect diseases in asymptomatic stages, thus telling growers earlier that their trees are infected, he said. An unmanned aerial vehicle – or drone — with a multispectral camera can cost between $3,000 and $8,000, Ampatzidis said.

The new study is published in the journal Computers and Electronics in Agriculture.


By: Brad Buck, 352-294-3303,

The mission of the University of Florida Institute of Food and Agricultural Sciences is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS works to bring science-based solutions to the state's agricultural and natural resources industries, and all Florida residents. Visit the UF/IFAS web site at and follow us on social media at @UF_IFAS.

avocado body rot1
avocado body rot1

avocado body rot1
avocado body rot1

Posted on Friday, February 22, 2019 at 6:16 AM
Tags: avocado (272), drone (2), spectral analysis (1)

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