- Author: Ben Faber
What a difference a few days can make in the life cycle of a fire. In this particular case, the Thomas Fire that is ongoing in the Ventura County around (and surrounding) in Southern California. The following images were taken by the Terra and Aqua satellites on Dec. 16, 17, and 19, 2017, and during those times fire conditions improved visibly. A difference in winds, in humidity, in the ability of firefighters to control the fire's perimeter, and in the amount of fuel left for the fire to consume can bring a raging fire to heel. This does not mean the fire cannot gain strength again if conditions worsen, but it is heartening to realize that weather conditions can allow firefighters to get a better handle on events as they have in the last few days.
This the the Thomas Fire on December 16, 2017 as seen by the Terra satellite. There were multiple areas of "hot spots" where the satellite indicates the fire is and where telltale smoke also pinpoints fire spots. These areas are numerous and the clouds of smoke coming off the flames are all consuming.
By December 17, 2017, conditions had obviously changed for the better and the fires were able to be somewhat contained. This image taken by the Aqua satellite on December 17, 2017, shows a much more subdued Thomas Fire. There are still hot spots visible but the number has vastly improved.
By December 19, 2017, hot spots are not showing up via satellite instruments. This does not mean the fire is completely out, but large hot spots are no longer detected by satellites. So, too, the copious smoke that was spewing from the fires is no longer in evidence. This Aqua image shows a much calmer landscape due to improving weather conditions at the time.
Per Inciweb today, the Thomas fire is 60 percent contained at present. At 272,000 acres, the Thomas Fire is now the second largest fire in the recorded history of the state of California. Unfortunately, weather conditions that allowed the fire to be contained to the 60 percent mark are destined to change as weather conditions deteriorate this afternoon. Inciweb reports that a forecasted strong north wind event will bring wind conditions similar to those experienced when the fire made its push into Montecito. With the introduction of these winds, critically dry fuels will be highly receptive to fire spread. During Santa Ana wind events three things happen: the weather warms, winds pick up, and humidity drops precipitously. All of these events promote fire growth. The Thomas Fire has experienced winds exceeding 70 miles per hour, temperatures in the mid 80's and humidity below 10 percent.
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NASA image courtesy NASA Worldview application operated by the NASA/Goddard Space Flight Center Earth Science Data and Information System (ESDIS) project. Caption by Lynn Jenner with information from Inciweb.
- Author: Gary Bender
This is from past experience, and is still relevant. Availability of replant trees is a major issue to consider at this point.
The wildfires in San Diego and Ventura Counties during the fall of 2003 were certainly devastating to many avocado groves adjacent to burning native chaparral. Many of the avocado trees were singed in the canopy without extensive damage to the large scaffold branches; these trees will re-grow new foliage with some relatively minor pruning to clear out smaller dead branches. However, other groves have had extensive damage, complete with charring of the bark in the trunk and boiling of the sap through the bark of the trunk. In these cases, the sap became hot enough to steam the cambium layer (the layer of living cells just beneath the bark), killing the tree above the soil line.
In the latter case, the tree above the soil line is dead, but the roots are still alive. Beginning about the first of March 2004, we have noticed that many of these trees are sending up rootstock suckers near the trunk. If left to grow un-grafted, these suckers will become an avocado tree, but not a known cultivar. The question is: should these burned trees be removed and replanted with a new tree? Or should a sucker be tip-grafted back to a known cultivar?
Sucker grafting in avocado is a well-known practice and has been used extensively in the industry when a grower desired to change cultivars. Generally, the tree is cut down leaving a threefoot stump, which is used as a stake for the new tree. A strong sucker growing from the base of the tree is selected (the sucker should be about 3/4 to 1" in diameter and stiff, not rubbery), and the other smaller suckers should be removed. The sucker is cut with a horizontal cut about 6-8" above the soil line, a 2”vertical slit is made down through the center of the sucker, and 3" to 4" long piece of budwood, cut like an arrowhead at the bottom end, is slipped into the slit, matching the cambium layers together on at least one side, and preferably on both sides. The graft is wrapped tightly with grafting tape, and the entire budstick is wrapped with Parafilm to prevent moisture loss, and grafting tape is used to tie the new grafted sucker to the stump (used as a stake).
Advantages from sucker grafting (as opposed to planting a new tree).
- Sucker grafting is cheaper. As recently quoted by a grafter in Fallbrook, sucker grafting usually costs about $2 per tree after the tree has been cut down to a 3 foot stump. If the grafter supplies the budwood and grafting tape, the price will probably be $2.50 per tree. If the grafter has to travel away from Fallbrook, the price will be higher according to the distance traveled. A new replacement tree will cost about $14 on a seedling rootstock, or $19-22 on a clonal rootstock. The labor cost for planting the new tree would be about $2.00 per tree. These costs do not include cutting down the older burned tree, or follow-up care for the young tree.
- The older, burned avocado tree has an extensive root system with a lot of stored energy. When the sucker graft begins to grow it usually grows very rapidly, much faster than a young replant tree. The sucker grafted tree should start to set fruit two years after grafting.
Disadvantages from sucker grafting.
- We are assuming that the sucker-grafted tree is healthy and does not have root rot or some other disease. If the older tree has root rot, it would be better to remove the old tree and replant with a new tree grown on one of the newer root-rot tolerant clonal rootstocks.
- In the system described above, the trunk is used as a stake. When the new tree grows enough to be selfsupporting, the old stump should be cut down close to the ground. The stump should be slightly sloped to drain water away from the new tree. This takes some careful chainsaw work.
- Suckers. Until the new tree gains strength and starts to shade the old stump, there will be other suckers emerging. These must be removed or they will take over and shade the grafted sucker.

- Author: Ben Faber
The destruction after a fire can be pretty gruesome and sad. Many times, though the fire moves through the orchard so fast that, even though the canopy has turned brown, there is a good chance the trees can come back. It all depends on how much damage has been done to the trunk. If the fire has substantially damaged the base of the trunk, it is unlikely to come back, even if the canopy is still green. That is the saddest thing, because you think you've dodged the bullet, but if the trunk is too damage, the canopy collapses gradually over a few weeks. However, the canopy may look a goner, but if the trunk is still intact, the tree will come back and may still be as productive as before.
The thing to look for at the base of the trunk is the discoloration. If it's black, it's probably not coming back. However, it can come back if after a few weeks you don't see the pencil-sized cankers that indicate that the sap has bubbled to the surface (see photo 1 below). If after a few weeks, the trunk is still clear of those bubbles (photo 2), even though the canopy looks gone, it is quite likely to come back.
It's also possible that the trunk may be damage in just one part of the trunk and not on the rest. In this case, it can also come back. The problem with these ones, is that they may come back and given enough time will be good trees again. But if they haven't recovered enough and there's a sudden heat spell, they may go down suddenly as if they had been burned again. That's the way they will look, like they have been burned again. Given enough time, though the avocado will grow from good areas to cover the poor areas and the tree may be productive again.
Avocados are amazing in their ability to recover. Eucalyptus can do it. But you singe the trunk of a lemon, and good-bye lemon.
Fire Information:
http://ceventura.ucanr.edu/Agricultural_Threats/Fire_Information/
Photo 1. Trunk damage with "boils" appearing indicating damaged green tissue below.
Photo 2. Heat damaged canopy but clear trunk with no damage.


- Author: Sonia Rios
Sonia Rios, Area Subtropical Horticulture Advisor, Riverside & San Diego Counties
Henry Herrera, Forester, California Department of Forestry and Fire Protection (CAL FIRE)
Gary Bender, Subtropical Horticulture Advisor, San Diego County
This is a reposting of a blog from 2015 that is still pertinent today.
Vegetation Weed Management
Vegetation weed management is something CAL FIRE feels strongly about, especially during times of drought. CAL FIRE interprets this type of weed management as a fuel reduction or fuel modification practice which helps growers create defensible space around their habitable structures or groves. Defensible space is a buffer between property (i.e. homes, groves, infrastructure) and plants (i.e. brush, trees, etc.) or other items surrounding the property to be protected that could catch fire and act as fuel.
Defensible space is needed to slow the spread of a wildfire and improves the safety of firefighters defending properties. Defensible space reduces the fire risk and creates space that firefighters can use as a tool to work safely and suppress a wildfire and to defend a structure or other property in the event of a wildfire. Fuel modification/reduction projects include defensible space around structures, fuelbreaks along roads and groves, ridge tops, or around property lines and other fire fuel reduction activities that lessen the risk of wildfires to communities. Fuel reduction projects usually remove cut vegetation from the site either through burning or haul-away methods. Fuel modification projects usually leave the cut vegetation on site in the form of wood chips or scattered material. These types of projects break up the lateral and horizontal vegetative continuity which reduced rates of fire spread, fire intensity, and flame heights which increase firefighter's chances of suppressing fires.
Prunings piled in draws within or around the groves can also be particularly damaging because they are dried vegetation which pose an increased fire danger due to the fact that piles of vegetation can easily ignite and smolder for a long time creating a challenge to firefighters. Vegetation that is piled in draws or other waterways can also obstruct water flow during rain events which could lead to erosion and flooding.
How to Keep our Growers and Groves Safe
Preventative Measures:
These preventive measures can be suggested for groves in areas of high fire hazard are often counter to other measures which might reduce erosion or improve root disease control, so a balance should be strived for (Goodall 1965):
1. Remove all combustible material from around the trunks of the trees for a distance of two to three feet.
2. Prune off low-lying limbs, those that are low enough to accumulate more than the normal inch or so of leaf mulch.
3. Remove from the orchard all broken limbs, deadwood and other combustible debris.
4. Clear brush, trees and other heavy vegetation away from edge of orchard for a distance of at least 50 feet.
5. Do not pile brush or other combustible material in draws or canyons, or around the edges of groves.
6. Apply sprinkler water for as long a period in advance of the fire as possible so as to have everything wet. Water during the fire would obviously be desirable but often is lacking because of lack of pressure or speed of the movement of the fire.
7. Use steel pipe and risers for above ground sprinkler systems.
Growers can also look for other tips on preventive measures on the Cal Fire website: http://calfire.ca.gov/fire_prevention/fire_prevention.php.
After a Fire
It is nearly impossible to determine the extent of damage to the wood of the tree immediately after the fire. The most critical part of the tree is the main trunk. The bark from just above the ground to about two feet high can become hot enough to kill the cambium, the growth layer between the bark and wood. When the cambium is killed, the tree is girdled and will die (Goodall 1965). Suckers will eventually grow from below the graft union of these trees; these suckers can then be grafted to an appropriate variety. However, many trees in the grove may still be alive internally because there was a quick burn through the grove, or the leaves merely died from heat generated by burning surrounding trees, vegetation and mulch (Bender 2012).
According to Bender (2012), fire damaged trees that have leaves that are completely brown do not use water, but there may be trees that have escaped the fire in the irrigation block and these need to be irrigated as soon as possible. The first thing to do is to repair the irrigation system. Risers, sprinklers, pressure regulators and poly-hose on the ground are probably melted and should be replaced as soon as possible. PVC pipe that is buried underground is usually fine, depending on its depth and fire intensity. If part of the trees in the irrigation block are alive and partly damaged, it would probably be best to roll out poly-hose onto the damaged trees and set up a separate irrigation block. As the trees recover and start using water, you can eventually go back to the permanent system.
Trees that are heavily damaged do not use as much water (therefore transpiration is reduced significantly), but their feeder roots need to be watered and short irrigations should occur to replace water evaporating off of the soil surface. Start with a one hour irrigation and monitor the soil closely, irrigating too heavily could lead to the onset of root rot. Do not irrigate damaged trees on its original schedule; a ten hour irrigation will not “force” the trees to grow back sooner, and roots could be easily damaged by lack of oxygen in the lower soil profiles due to water accumulating and the soil becoming saturated.
Every fire is different, so experiences vary. It may take several months to be able to observe whether the bark is killed all the way to the cambium or not. Thus, we recommend against pruning until new growth appears to indicate where the wood is alive. According to Bender (2012), an alternative method which is rather unique to the avocado industry, the burned trees can all be stumped immediately and allowed to re-grow. “Stumping” is a normal practice in the industry when avocado trees have reached such heights that fruit is high off the ground and picking becomes difficult. In many of the groves that were burned, stumping was probably needed anyway; therefore after a burn stumping would be a reasonable alternative for many growers.
Fire damaged trees should be whitewashed on the south side of the limbs. Goodall (1965) also suggests to save expenses, fertilizer and pest control can be postponed for a year or so.
According to Bender (2012), if the goal of the grower is to bring trees back into production as soon as possible, the avocado tree will usually recover production faster if the grower is patient and prunes only the dead wood three months after the fire. Unfortunately, this practice creates a permanent problem in the grove as far as irrigation scheduling and application. Mixing full-grown trees (untouched by the fire) with partially pruned trees (and stumped trees) in an irrigation block means that some trees will be over-watered, or under-watered, depending on their size. Adjustments can be made in the sprinkler sizes, but generally this is an undesirable cultural practice due to every tree needing a different rate of irrigation and can this can also add to labor and equipment costs.
If the goal is to reduce the size of all trees in the irrigation block to a manageable size, then stumping the block immediately after the fire is the best solution. Trees will be out of production for two years and have about 50% production in the third year, and some re-grafting may have to be done, but fertilizing and watering properly is manageable.
A third option could be to scaffold all trees in an irrigation block to 12' in height. This would get rid of a lot of dead wood immediately, and might allow the trees to come back in production faster than the stumping the trees.
It is helpful for growers to know the value, for insurance purposes, of trees that are lost due to fire. Determining the value of a tree in an orchard is not a simple matter because one must take into account the income lost if the tree had been producing, as well as the costs of planting and maintaining the new tree. Also, the income from the new tree, once it comes into bearing, helps to defray the costs involved in bringing the tree to maturity. Examples can be seen here at the UCCE website: http://ceventura.ucanr.edu/Agricultural_Threats/Fire_Information/. Assessing tree loss can be calculated at the UC DAvis Ag Econoimics website: https://coststudies.ucdavis.edu/en/tree-vine-loss/
Record-low rainfall, extreme heat and a statewide drought has caused a significant increase in wildfires and a need for Californians to participate in fire-prevention tactics, including growers. According to CAL FIRE, in order to prevent wildfires and property damage, homeowners are asked to maintain “defensible space” around their house and groves year round and not use powered equipment outdoors when it's hot, dry or windy. Wildfire prevention such as defensible space, keeping properties cleared of dried vegetation, and public education is the best long term solution.
Photo 1: An inmate firefighter crew battles a fire in an avocado grove outside Fallbrook, California, May 14, 2014. Photo: Sandy Huffaker
Photo 2: Low intensity fire damage on avocados. Photo: U.S. Today
Photo 3: A CAL FIRE inmate crew fighting a wildfire in an avocado grove, May 2014. Photo: Sandy Huffaker
Work Cited
Bender, Gary. 2012. Recovery from Fire Damage in Avocado Groves. UCCE San Diego Website: cesandiego.ucanr.edu/files/54279.doc. [Accessed June 16, 2015].
Goodall, G. E. Avocados and the Coyote Fire. California Avocado Society 1965 Yearbook 49: 81-83.
Ventura Co UCCE publication. Calculate Cost of Fire Damage to Avocado and Citrus Trees. Growing Avocados in Ventura County Reference Book. UCCE Ventura



- Author: Ben Faber
Fire Information
Tree and Vine Loss Calculators
Spread sheets to help you calculate loss
Calculate Cost of Fire Damage to Avocado and Citrus Trees
Information from Ben Faber, Soils and Water, Avocado and Minor Subtropicals Advisor
Information on how to care for fire damaged trees from Ben Faber, Soils and Water, Avocado and Minor Subtropicals Advisor
Information on fire ecology and fire safe landscaping for homeowners, developed by Sabrina Drill, Natural Resources Advisor
UC Center for Fire Research and Outreach
Information on fire science from UC experts. Includes information on how to make homes and other structures more fire resistant, developed by Steve Quarles, Statewide Wood Performance and Durability Advisor
Local Fire Departments - have regulatory information you may need
Ventura County
City of Ventura
City of Oxnard
City of Fillmore
City of Santa Paula
Santa Barbara County
City of Lompoc
City of Santa Barbara
City of Santa Maria
Publications Available From University of California ANR Catalog
You can find the publications listed below at theUniversity of California DANR Catalog site (In the ANR Search type fire) and order more than one publication at a time or you may click on one of the links below.if you purchase a priced publication enter the promotion code PRVEN56 at check-out. You'll receive a 10% discount on your order, and a portion of the sales will benefit local programs.
A Property Owner's Guide to Reducing Wildfire Threat - describes ways homeowners can reduce the threat of fire to their property. Cost $1.50
Home Landscaping for Fire - Incorporating fire safe concepts into your landscape is one of the most important ways you can help your home survive a wildfire. FREE
Landscaping Tips to Help Defend Your Home from Wildfire - You can have both a beautiful landscape and a defensible fire-safe zone. FREE
Recovering from Wildfire - discusses issues that family forest landowners should consider following a wildfire. Cost $5.00
WildFire: How Can We Live With It? (DVD) - This program contains general information about wildland fire in California. Cost $20.00
Companion Set: How Can We Live with Wildland Fire? (Publication and DVD) - What role does fire play in the natural cycle and what choices can we make about coping with wildland fire? Cost $27.50
How Can We Live with Wildland Fire? - What role does fire play in the natural cycle and what choices can we make about coping with wildland fire? Cost $10.00
