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UCCE Ventura County- Blogs
Avocado Cankers
Avocado Trunk Cankers
This has been a low rainfall year, and often with the low rainfall, cankers will seem to suddenly appear on the woody parts of the tree. There are a number of causes for the white exudate from cankers on the trunk and limbs of avocado. Any wound will cause the tree sap to run and crystalize on the surface. It is a seven carbon sugar of mannoheptulose, or its alcohol form perseitol. It's sweet. So any wound that might be caused by woodpeckers or little kids climbing the trees will damage the bark, and where the damage has occurred, the sugar will form. There are also diseases that can cause a wound that will exude the sugar. Three of these are due to water stress of some form that allows infection to occur. One of these is bacterial – Bacterial Canker. Another is caused by a fungus which in the past was called Dothiorella Canker. We now know it by a different name and a UCR plant pathologist has actually identified seven different species of fungus that invade the wood and can eventually weaken the tree so limbs can break and the tree becomes unthrifty. In the case of very young trees, they can be killed by the fungus. A third cause of sugary cankers is Black Streak, the cause of which was unclear until recently when Dr. Akif Eskalen possibly identified it. It was coming from a similar set of fungi that cause Dothiorella Canker. It makes sense, because in all three of these cases, they most often appear after a low rainfall year, where pressures in irrigation systems are insufficient, where emitters have clogged and where water or salinity stress have occurred. The bacteria and fungi that cause these cankers are widely distributed in most orchards and are just waiting for the stressed tree to appear. The grower just needs to identify where this stress is occurring, correct the problem (clogging, low pressure, poor irrigation design, infrequent scheduling, inadequate leaching, etc.) and if the damage is not too extensive, often these symptoms will disappear with time.
The fourth cause of canker is caused by Phytophthora citricola, a relative of avocado root rot. This is caused by a moist trunk, either from irrigation water hitting the trunk, or on the north side of the tree that doesn't dry out from morning dew. This is a much slower acting disease than root rot, although it can rapidly kill young trees. The cankers occur at about 18 inches from the ground and gradually girdle the tree. The first thing to do before ever seeing this disease is to make sure irrigation water isn't hitting the trunks. If cankers appear, they respond to the same materials used for root rot, but should actually be sprayed right on the canker.
Images
Top: Black Streak can occur on trunks or branches as small, scattered cankers. The name comes from the blackening that occurs around the infected area.
Next: Bacterial Canker causing discrete silver dollar-sized cankers. The exudate running down from the bottom edge results when a knife is poked into it. The cankers tend to run in a line up the trunk or branch.
Next: Citricola crown rot with the cankers girdling the trunk. It appears near the ground.
Bottom: Dothiorella Canker (soon to have a new name) can occur anywhere on the trunk or branches
black streak
bacterial canker
citricola
dothiorella canker
New UC Report on Water
Bold moves needed for California agriculture to adapt to climate change
University of California report details farming's needs for climate resilience
California should take urgent and bold measures to adapt its $59 billion agriculture sector to climate change as the amount of water available for crops declines, according to a collaborative report by University of California faculty from four campuses.
Published in the Proceedings of the National Academy of Sciences, the report provides a roadmap for more water capture, storage, and distribution systems that are in harmony with climate projections and ecosystems. It further considers how runoff and groundwater can be used repeatedly as it flows generally from mountainsides to coastal lands.
“The availability of water for consumption is decreasing because of climate change, partly due to increased evaporation and transpiration but also because we don't have the system set up to capture and use the larger and more variable flows that are now the norm,” said Kurt Schwabe, a public policy professor at UC Riverside and co-author of the report.
A warmer planet means fewer but larger rain and snowstorms in California. The rising temperatures and shorter winters also result in smaller volumes of water stored in mountain snowpacks that have historically replenished California's reservoirs each spring. And a greater amount of water is getting lost through evaporation.
This means that agriculture, which uses about 80 percent of the water consumed in the state, will need to adjust to a future with less water available for irrigation.
To help reduce the overall impact on agriculture and society from climate change, the report's authors envision a more nimble and responsive system that can capture and store water from big storms before it goes to sea to prevent floods and keep crops growing through the hot, dry summer months.
To do so, California must increase its water storage capacity, but that doesn't necessarily require building more dams and reservoirs, Schwabe said. Great storage capacity now exists in the state's depleted aquifers below the Central Valley and the coastal plains.
“It's really a huge win,” Schwabe said. “We can start taking more of those flood flows, and unexpected overflows, and put them in these groundwater aquifers. We've got plenty of capacity there, and you don't suffer from the evaporation rates that you do with the surface reservoirs.”
Capturing the flows would involve diverting torrents from heavy rains and accelerated snowmelts to farm fields or to habitat lands where controlled flooding would cause no harm, and the water would percolate down to aquifers. Farmers would then have more groundwater to get through drier periods while also reviving wildlife habitats.
Farmers also should take advantage of new crop varieties, so they have more flexibility to deal with different water situations. Changing crops, unlike changing irrigation systems, is a practice that can lead to reduced overall water use.
“It's obviously an economic decision confronting the growers,” Schwabe said.
However, switching from a water-intensive practice such as flood irrigation to something like drip irrigation, doesn't necessarily save much water at the system level, he said. Flood irrigation may be appropriate if it helps recharge aquifers, or the runoff is used again by other farms.
“Sometimes the runoff water appears later in the system for use,” Schwabe said
California also needs to build more flexibility into its water delivery systems. The state's three major aqueducts — the California State Water Project, the Central Valley Project, and the Colorado River Aqueduct — for the most part transport water from north to south. A greater ability to move water from east to west and vice versa would allow for more efficient water use. Farmers who have more water than they need for a particular season could sell to others in need. With prices based on scarcity plus delivery costs, such a marketplace would have incentives for storage and efficient use, Schwabe said.
The report's title is “Cultivating Climate Resilience in California Agriculture: Adaptations to an Increasingly Volatile Water Future.”
In addition to Schwabe, the report's co-authors are Josué Medellín-Azuar at UC Merced, Alvar Escriva-Bou at UCLA, and Amélie Gaudin and Daniel Sumner at UC Davis.
“When I moved to California over 20 years ago, someone told me, “Don't let people tell you there isn't a lot of water in California because there is. The problem is that it's just managed really poorly,” Schwabe said.
That said, Schwabe believes the state is making progress by developing policies that can lead to more efficient and sustainable outcomes, such as the Sustainable Groundwater Management Act of 2014.
“Today more than ever before we're seeing partnerships across environmental, agricultural, and municipal sectors to address water scarcity issues,” Schwabe said. “And that's a good thing.”
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waterfall
Non-chemical Weed Control
This is a website designed for wildlands weed control, but the practices fit right into those of orchard crop grower, as well
Methods for Managing Weeds in Wildlands
Weed Control User Tool (WeedCUT) -
https://weedcut.ipm.ucanr.edu/#gsc.tab=0
This decision support tool provides land managers with guidance on a range of methods for managing invasive plants in wildlands using non-chemical approaches exclusively, for situations when use of herbicides is restricted or not desired. The tool is intended to be developed further to include management practices including herbicides in the future. Explore all management practices below or enter the characteristics of your weed and your site to filter for the most effective practices. A manual containing all listed management techniques is available for free download. Biological control is currently not an outcome for the filtering tool but can be accessed directly through the thumbnail grid below. An Executive Summary provides summary information about using non-chemical methods at a programmatic level.
Filter by plant and site characteristics
View management practices by select plant species
The Manual from CAL -IPC (California Invasive Plant Council), has many more details. This manual provides comprehensive descriptions of 21 commonly used non-chemical weed control techniques and of biological control agents for 18 weed species/species groups that will help you as a practitioner treat weeds more effectively.
Authors of each chapter have compiled research and on-the-ground knowledge of subject experts on tools and methods of application, as well as on efficacy of techniques under various environmental conditions and across different classes of invasive plants. Environmental, cultural, and human safety risks are also highlighted to help support safe and effective use of techniques. This manual is designed to be a go-to resource for practitioners that are either complementing their weed control work with non-chemical techniques or are exclusively restricted to not using herbicides. Individual BMPs will be incorporated into an online decision support tool still in development.
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Weed control bmps manual
CA Avocado Acreage Expands
Each year the California Avocado Commission partners with Land IQ to produce a Statewide Avocado Acreage and Condition Analysis report utilizing digital satellite imagery, aerial photography and analytical tools to survey California avocado groves. This data helps the Commission make informed budgeting and marketing decisions and provides industry members with spatial data concerning crop type, location, condition and density. See the full 2023 Report HERE.
According to the report:
- In 2023 there were 52,534 planted avocado acres
- The majority of growing acreage is located in Ventura, San Diego, Santa Barbara, Riverside and San Luis Obispo Counties with a total of 50,818 planted acres
- The five top-producing counties reported 1,059 new/young acres and 3,399 topped/stumped acres
The report also provides acreage data by zip code, county, condition, year planted and density.
The California Avocado Commission's crop estimating team in conjunction with Land IQ uses the latest in remote sensing techniques to assess avocado acreage in production. As technology continues to advance refinements in our fourth generation of remote sensing techniques were applied to satellite imagery collected during spring and summer months. The imagery processing techniques include; segmentation into homogenous polygons, retention of tree crop polygons, calculation of average crop canopy moisture and vegetation indices, analysis of change maps from previous inventories, and classification of avocado groves into four categories; producing, topped/stumped, new/young, and abandoned. Aerial imagery (for a real-world view), and satellite imagery (for spectral and temporal data) are integrated into previously classified avocado acreage and analyzed for current condition of California avocado acreage statewide.
avocado farm 1925
Ag Labor Workshops for Employers and Supervisors
Ag Labor Management Education Program:
General Descriptions and Dates
Ag employers and their supervisory staff must remain informed of new labor laws and regulatory requirements to protect workers, their operations and their assets. The Ag Labor Management Education Program will help agricultural employers, HR managers and their field supervisors to better understand and comply with numerous requirements using a two-tier approach that includes a series of seminars and workshops as described below:
Ag Employer Seminars
Three seminars will be offered in English by labor experts including attorneys and enforcement agency representatives to provide updates and guidance on key issues impacting agricultural labor.
Topics include:
- wage and hour;
- union card-check elections;
- new worker health and safety requirements;
- paid leaves of absence;
- requirements and best practices for H2A Visa workers, and
- a range of other potential issues and liabilities.
Registration Fees per Person: Early Bird-$60; Late-$75; Walk-in*-$95
* Walk-in registration dependent on space availability.
Dates and Locations:
August 14, 2024 |
San Diego County Farm Bureau Escondido, CA |
Register |
February 19, 2025 |
Santa Maria, CA | |
March 5, 2025 |
Coalinga, CA |
Ag Labor Supervisor Workshops
Five training workshops will be offered in Spanish by highly experienced bilingual instructors to help supervisors learn about their critical roles and how to better manage and communicate with employers and workers.
Supervisors will learn to:
- implement required policies and procedures;
- to foster employee retention; and
- more effectively prevent and manage -
- work injuries,
- harassment claims,
- union interventions, and
- wage and hour issues.
Registration Fees per Person: Early Bird-$50; Late-$60; Walk-in*-$80
Note: Please register early - Space limited to first 60 registrants.
* Walk-in registration dependent on space availability.
Dates and Locations:
August 15, 2024 |
San Diego County Farm Bureau |
Register |
February 5, 2025 |
Palm Desert/Coachella, CA |
|
February 6, 2025 |
Imperial, CA |
|
February 20, 2025 |
Santa Maria, CA |
|
March 6, 2025 |
Coalinga, CA |
workers in the field