- Author: Ben Faber
Laurel Wilt Disease has been on the radar since 2002 when it became apparent that trees related to avocado were dying in the Georgia area. The Lauraceae family comprises a major portion of the evergreen tree species in the southeast. It's a fungal disease spread by the red bay ambrosia beetle. Since its introduction, the pest/disease complex has spread throughout the Southeast US, causing significant death and economic loss in forested areas. Since about 2011, it has been causing significant damage to the avocado groves in the Miami area. A massive amount of energy has been put into studying the control of the disease, but as yet, there are no clear solutions once a tree is infected. Tree removal is the answer to contain the spread.
This is a grower letter describing the frustration of dealing with Laurel Wilt Disease in Florida and an alert to California growers to get prepared for it.
Homestead, Florida
(305) 972-9499
cdlt1948@yahoo.com
DLT Farms LLC
October 27, 2019
Open Letter to Avocado Producers:
I grow tropical avocados commercially in Homestead, Florida. That's been my passion for the last 16 years, The last five years have been a frustrating nightmare caused by Laurel Wilt. This morning I marked three more trees for extraction in addition to the 10 trees I marked three days ago. I lose about 20-25 a month and it's on the rise.
The largest avocado-producing areas are free of the problem at the moment. In South Florida, tropical avocado is a very small industry with little economic and political influence, as a result not much attention is paid to this crises. In the Homestead, Florida avocado region the pathogen and vectors are everywhere. There are orchards that disappear from one year to the next. Unfortunately, we have been on the front lines of this disease.
This creates an opportunity for the rest of the avocado producing areas, so far free of this disease to do research in this area. There is a lot of research to be done and as time goes on we gain more experience. Here, there is access to adult trees in the field for testing and research. This is not the case for areas in which the disease has not made its appearance.
I only mention some investigations that could be pending:
Some trees die in a week, however there are trees that look resistant to Laurel Wilt, they have tested positive from root to canopy, proven on multiple occasions and methodologies, yet they are still alive and show no symptoms of the wilt. I know of two, one in particular I call 9-7, is positive since January 2019 and continues alive and recovering. Personally I think this tree is talking to us, however there are no funds to see what it tells us.
Early detection in the process is vital to early removal of diseased trees, before other trees acquire the disease. It is essential to determine whether the tree is contaminated with little pathogen, to extract it before it contaminates adjacent trees. There is no data on the time between when a tree is contaminated and when the first sign of "sadness" becomes visible. Less than a week ago I detected a little sadness in a branch. When cutting it, it looked positive for wilt, I continued to check three more trees on the same row and all three tested positive at various levels without visible symptoms. Root contamination moves unnoticed for weeks or months. This type of root contagion remains an observable presumption of farmers and has not been investigated.
Some producers believe that there are two or more strains of the fungus that causes the disease, (Raffaelea Lauricola), one much more aggressive than others. A full DNA study is complicated and costly. As I understand it, it hasn't been done and there are no plans.
Other producers began doing thermal treatments on infected and stumped trees. I tried on 8 of my trees. All are alive and doing well, the two oldest are 17 months old and continue to grow. On the other hand, the eight have tested positive for Laurel Wilt, post-treatment. There is no scientific data to understand what is going on and what opportunities this offers.
What attracts vectors and what can farmers do? Many growers are gaining experience of their own. I stopped injecting phosphorous acid to treat Phytophthora because I have noticed that these trees have a higher frequency of vector inoculation than others not injected. I suspect why, but we don't have a scientific foundation to know what's going on.
Can trees be vaccinated with some form of vaccine to increase resistance or defense against the pathogen?
And so on, I could mention a lot more.
Looking back we knew it was coming, but we didn't prepare enough, partly because it wasn't always easy to test in the field and there were a lot of restrictions on conducting test in greenhouses and we just didn't believe it or wanted to invest funds in research. Some thought it would never come.
We all see these bark beetles moving around the world with little or no restriction. One day any area can wake up to the bad news.
I can tell you this: you can imagine this disease in your grove, more or less we know what it does, you can read articles, watch YouTube videos, after you finish your imagination exercise, I can tell you as a grower dealing with this every day, MULTIPLY IT BY 10 !
Please, support research in the area where it can best be done. Get ahead of it.
Signed,
Carlos de la Torre
Keep abreast of Laurel Wilt Disease!
You can see presentations that have been made by a University of Florida research contingent which spoke to avocado growers this summer, 2019:
You can also hear a webinar about the pest/disease complex by UCR's Monique Rivera:
Photos: Symptoms of Laurel Wilt Disease in avocado. Distribution map over time of Laurel Wilt Disease in the Southeast. Image of Georgia forest affected by Laurel Wilt Disease.
- Author: Ben Faber
Boom, just when you think everything is going fine, you run across a reminder that there are little things going on in the orchard that are out of our control. In Goleta, I just ran across these crick-side, crook neck fruit that are a reminder that we just had about 3 weeks of foggy weather (in the fall, when it's supposed to be in the spring) and then a week of hot weather which is just the condition to create this calcium imbalance and distorted fruit. It's no big big deal, unless it was all over tree. Just more of an oddity. Harvest time is past this year so didnt expect to see it on this new fruit.
At avocado harvest time, growers are in the orchard checking things out a little more closely and to see what is going into the bins…..and they see some unusual shaped fruit. Here's what's been popping up and some possible explanations.
Crick-side - First described by Dr. J. Eliot Coit as kink-neck and later by Horne (1931) as kink-side. Finally, the name crick-side (Horne, 1934) was adopted. It is characterized by a definite depression on one side between the stem end and the larger portion of the fruit causing a distortion. In some cases, the area of depression turns black and the fruit drops. In other cases, the fruit grows and matures but the distortion remains. Crick-side is usually found on trees carrying a heavy load of fruit. It has been suggested that high temperatures or temporary water-stress may relate to the occurrence of crick-side, but no definite determination as to its cause has been made.
Carapace Spot - First described by Horne (1929), the name carapace-spot was chosen because of the resemblance to a turtles' back. This external blemish is corky and usually cracked into somewhat regular, angular divisions. The flesh under the carapace spot is undamaged, but exterior appearance is such that the fruit is reduced in grade. Slight rubbing or brushing of tender young fruit on leaves or stems appears to cause this corky growth to start. Fruit on trees exposed to strong winds are more apt to develop the trouble. Windbreaks should reduce injury in windy areas.
Photo: Avocado thrips damage, carapace damage and greenhouse thrips damage.
Sunblotch - This is a viroid that can affect fruit, leaves, and stems with a yellow or reddish streaking, cause a compacted growth and willowy growth habit. The streaking in the fruit is usually depressed and doesn't extend the length of the body.
Sunburn - Fruit exposed to full sun may be injured by sunburn. This occurs when trees defoliate, or partially defoliate, from any of several causes, leaving the fruit exposed. It is normally most severe on fruit on the south and southwest portion of the tree. Sunburn shows as a pale yellowish area on the exposed side of the fruit. Often the center of this area turns brown to black and may wither.
Ring Neck - This trouble has been observed occasionally, particularly with Hass. The cause is unknown but is believed to be related to soil-plant water deficiency at a critical time. A ring of tissue on the pedicel just above the attachment to the fruit dies, turns black and peels off. If only superficial, the fruit remains on the tree. Growth may be retarded because the restriction impedes movement of nutrients and water outward to the fruit. Most severe in humid coastal areas.
Embossment - Occasionally, and particularly on Fuertes, a section of the surface will be raised slightly or be a darker or lighter color. This is referred to as a sectional chimera or genetic mutation.
Healed over damage - if fruit has mild damage that allows it to heal over (remember avocado fruit expand by cell multiplication not enlargement), then a scar is left, such as this likely amorbia feeding
Cuke - As in cucumber but not a squash. These are seedless fruit that can most often be seen from a fruit set in cooler weather or due to some hormonal stimulus. We don't know the reason, but seems to occur more commonly along the coast.
Double Fruit - In some instances there may be a normal shaped fruit with a single cuke attached ot in some cases there is a double ovary and two fruit are attached.
Woody Avocados - For some unknown reason, avocado fruit will form into a grotesque woody structure hardly resembling an avocado. The cause is genetic and non-transmissible.
Sources: R.G. Platt - California Avocado Society Yearbook 1972-73 and Reuben Hofshi and M.L. Arpaia Yearbook 2002.
- Author: Ben Faber
The California Avocado Society held its 104th Annual Meeting recently and acknowledged an individual's contributions to the avocado industry with its Oliver Atkins Award. This award is presented in honor of nurseryman Oliver Atkins who went beyond what was required or expected, benefitting the avocado industry and its growers. His devotion to the industry was noted in his day-to-day activities and to the changes that he brought to the industry. The award was made to Mr. Pablo Rodriguez.
The award was presented by Nurseryman Rob Brokaw and the following notes were made during the address:
Pablo Rodriguez was born in Mexico in 1950, one of eight kids. He attended a private school on scholarship from ages 8-12, finishing his formal education at 8th grade. He came to the US in order to support his parents and siblings at age 20 in 1971 and worked up and down California for two years before landing at an avocado/citrus nursery in Ventura county.
The nurseryman at the time made a point of “keeping an eye on Pablo”, and Pablo soon rose to be the nursery manger, developing an expertise in grafting. He bought a home in Santa Paula, raising a family there. He gained US citizenship in 1996. He and his family also have a company that performs topworking which is now managed by son Robert.
Readying a rootstock for a graft
As the nursery became involved in working with partners overseas, Pablo's expertise was in demand. He has worked with collaborators in Mexico, Peru, and Dominican Republic, Chile, Florida, Hawaii, Spain, South Africa and more.
His skills and expertise are evident in the millions of avocado and citrus trees that have been produced here in California under his watchful eye, but the greater impact of his efforts resonates around the world.
Pablo and Samuel Garibay showing South Africans the Brokaw Way
Today Pablo is in semi-retirement. In his case, that means he works just as much as he ever did. He's constantly operating in the background shoring up processes and ensuring smooth operations. On Sundays, he can be found wandering the orchards – “just making sure the graftwood is good for harvest this week!” He isn't asked to do this; he just does it because it needs to be done.
But the real story about Pablo, apart from his intelligence and his accomplishments, is his profound humility and humanity. Pablo's dealings with others are informed by a deep spirituality and morality. He seeks to raise others, preferring to remain in the shadows.
Pablo is a guy who, when asked if he can do the impossible, will think for a while, then shrug and say, “Well, it has to be done”. And then does it. This happens regularly.
To his family, to California growers and to the global avocado industry, Pablo has given selflessly of himself. We're all enriched by his presence in our community.
A Serious budman
- Author: Ben Faber
California Avocado Society's
2019 Annual Meeting
Mature high-density plantings and pruning - what happens over time!
- Author: Ben Faber
It's so nice to be able to find a way to rapidly answer homeowner questions. Once one questions has been addressed, invariably another one pops up. There are mysteries to plants and they can go on and on forever. The University of California Cooperative Extension has locally trained volunteers to answer the questions that local homeowners are going to ask about local plant problems. You can find Master Gardener contacts by going to the map to find a local office and the local MG Helpline: http://ceventura.ucanr.edu/Offices/
Recently I got an email from a homeowner that had a burning question about the name of an avocado found in a picture. That one question lead to another and to another and eventually to how to plant a tree in a heavy clay soil. i was going through explanations, and suddenly remembered a website put together by Greg Alder with photo steps going through the whole process: http://gregalder.com/yardposts/how-to-plant-and-stake-an-avocado-tree/
After passing that link on to the homeowner, I havent had any more questions about planting avocados. The site does the trick.
So if you are looking for more answers about avocados, the Annual Meeting of the CA Avocado Society is October 4 - next month. Come on the tour and see how it's done:https://californiaavocadosociety.org/annual-meeting.html
Filling a planting hole to see if water drains well enough before planting an avocado. A great photo from the blog.
