The very fact that avocados can be grown in hard to get to places means that the trees are also in areas that are subject to wildfire damage. Recently several hundred acres of avocado burned in the foothills. The fire was fanned by high winds and low humidity.  

Every year there are avocado trees that burn, either through careless attention to early morning fires that pickers build, wildfires or car accidents. A grower needs to be patient and observant to bring the trees back into production.

Although injury to foliage and young growth is visible within a few days of the fire, the full extent of the damage may not be known for several months or possibly the next growing season. In the case of severe injury, die-back may continue to occur for several months after the fire. New growth that occurs after the fire may suddenly collapse the following year when the growth is tested by Santa Ana conditions.

The important rule to follow after a fire is to do nothing - don't prune, don't fertilize and maybe don't water. Or rather, water very carefully. Dry winds may have sucked the water out of the ground and may need to be replenished. The fire may have burned the irrigation lines and need to be replaced.

The need to immediately replace irrigation systems will depend on the time of year, the extent of damage, the soil moisture after the fire, the weather forecast, labor availability and many other considerations. It is not terribly expensive to replace hoses, but if PVC sub mains have burned, it will be a big job and it may not be necessary to jump on their replacement. Check the soil and the tree status before rushing to replace an irrigation system. It is on the list of things to do, but maybe not tomorrow.

In the meantime, if the tree has been defoliated by the fire, it has lost its ability to transpire water. Watering a tree with no leaves will set up those conditions that are conducive to root rot. Until the tree begins to leaf out, watch soil moisture to decide how much water the trees are pulling out of the soil. The emitters should be capped or plugged on some leafless trees. Then as the tree puts on new growth, shallow, infrequent irrigations should start. This may mean replacing the 10 gph microsprinkler with a 1 gph dripper if only a portion of the orchard has been burned and the rest of the trees need their usual amounts and frequency of water.

The avocado has a tremendous ability to come back from fire and frost damage. However, the tree will tell you where it is coming back. It will start pushing growth where the tree is still healthy. It may take 3 to 6 months for this growth to occur.

Delay pruning until the tree clearly shows where it is going to regrow. By waiting, you save the expense of having to return sometime later to remove more wood and also will be able to save the maximum about of tree.

An activity the grower can perform is whitewashing. The defoliated tree can be further damaged by sunburn after it has lost its protective cover of leaves. The upper surface of horizontal limbs and the south sides of exposed trunks are the most affected. The whitewash can delay the appearance of new growth, but it does not affect total growth. There is usually no value in applying the whitewash to small limbs.

There are various commercial whitewashes on the market.  The easiest to prepare is the cheapest white latex paint on the market mixed with water to the extent that it will go through a sprayer.

Avocado trees have a great ability to recover after fire damage. Even trees killed below the bud union will frequently develop into good trees if they are rebudded and given good care. Trees which do not put out vigorous sprouts should be removed. Interplanting avocados would rarely be advisable because of their rapid recovery.

Fire Information:

http://ceventura.ucanr.edu/Agricultural_Threats/Fire_Information/

For another version of fire recovery, go to: https://www.californiaavocadogrowers.com/cultural-management-library/post-fire-grove-recovery

Photos from Kevin Ball, firefighter/farmer

Ventura County Master Gardener

A blind lemonade and orange juice taste-testing trial was incorporated into a recent citrus grower workshop in Santa Paula. The topic of the meeting was lemon rootstocks and scions and the attendees were for the most part lemon growers. This seemed like an opportune time during the refreshment portion of the workshop to see what commercial lemonade and orange juices these professional growers might prefer. This would be an unreplicated trial, since it was only this one time with a small set of tasters, but might be give a sense of what citrus farmers prefer as their juice.

Four different orange juice brands and four different lemonade brands were chosen based on a range of prices. Two tables, one with lemonades and the other with orange juices, were divided into four sections labeled with Roman numerals, 1-4. A small amount of each juice was provided to the tasters in unmarked cups. The testers ranked their preferences on a grid with an 'A' though 'D' ranking beneath the corresponding Roman numeral label. “A” being the preferred juice and “D” being the least preferred. A paper label on the juice container temporarily concealed the juice's actual identity.

In this small,unreplicated trial, the most expensive juices did not have the greatest number of taster votes. None of the tasters expressed negative opinions about any of the juices, but there were definite preferences as can be seen by the tally. There's no accounting for growers' tastes, maybe.

ORANGE JUICE RESULTS, in order of preference:

Trader Joe's fresh squeezed orange juice; 16 votes; 8.6 cents/oz. 

Walmart store brand; 6 votes; 3.5 cents/oz.

Tropicana Original; 5 votes; 5.5 cents/oz. 

Simply Orange with pulp; 3 votes; 9.0 cents/oz.

LEMONADE RESULTS:

Simply Lemonade; 12 votes; 5.8 cents/oz.

Tropicana Lemonade; 10 votes; 6.8 cents/oz.

Minute Maid Lemonade; 5 votes; 2.3 cents/oz.

Newman's Own Virgin Lemonade; 3 votes; 5.6 cents/oz. 

We thank all who were involved in this survey and to the five Master Gardeners who have been involved in not only the organization of this tasting, but also the grower meeting and help in harvesting some of the lemon trials that were reported on at this meeting.

State by state export data

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:

Laurel Wilt Presentations

You can also hear a webinar about the pest/disease complex by UCR's Monique Rivera:

Laurel Wilt Talk

 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.