- Author: Ben Faber
Dr. Ramina Gazis, pathologist from University of Florida, will offer a seminar on her current laurel wilt research
Laurel Wilt-Ambrosia Beetle Grower's Seminar to update and discuss testing out-of-the-box control approaches research project. This project was supported by the Florida Avocado Administrative Committee.
Purpose: The Florida Avocado Committee funded a project to investigate the potential for inducing an immune response in avocado trees to infection by the laurel wilt pathogen. The purpose of this seminar is for Dr. Romina Gazis to update the avocado industry on the results of this research. This meeting is open to anyone to attend.
Date: May 27, 2021 (Thursday)
Time: 10AM-11AM (US Eastern Standard Time)
Location: Zoom – see below agenda for link
AGENDA
- Dr. Crane, Welcome and introduction
- Dr. Gazis, “Vaccinating” avocado trees: inoculating avocado trees with selected non-pathogenic fungi and denatured Raffaelea lauricola and their response to the virulent laurel wilt pathogen
- Questions and discussion
Jonathan Crane is inviting you to a scheduled Zoom meeting.
Topic: LW-AB Vaccinating avocado trees
Time: May 27, 2021 10:00 AM Eastern Time (US and Canada) which is 7-8 AM CA time
Join Zoom Meeting
https://ufl.zoom.us/j/96300665742
Meeting ID: 963 0066 5742
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Join by Skype for Business
- Author: Brittney Goodrich
By Brittney Goodrich, Assistant Cooperative Extension Specialist, Agricultural and Resource Economics, University of California, Davis
If you own or manage a commercial avocado orchard, you have likely debated at one point or another whether to seek out honey bee colonies to pollinate your orchard, and how much to pay the beekeeper for those pollination services. A recent academic paper published in the Journal of Applied Entomology summarizes findings regarding the role of insect pollination in avocado production, and I would encourage you to take a look, especially if you have not sought out honey bee colonies in the past (see Dymond et al., 2021 referenced at end of article). Dymond et al. conclude that “In 19 out of 23 studies, insect pollinators contributed significantly to pollination, fruit set and yield.” And “In most situations, growers will benefit from an increased density of pollinators.” However, they note that renting honey bee colonies may not make economic sense for every orchard. In this article, I'll touch on some factors that may influence a grower's decision to place honey bee colonies in avocado orchards for pollination services.
Are managed honey bee colonies needed in your orchard?
Given the conclusions of Dymond et al. (2021), if you are a grower who has not placed honey bee colonies in your avocado orchard in the past, this may be something to consider going forward. Though, doing so may not guarantee increases in yield because your orchard has likely been receiving pollination services from wild pollinators and/or honey bee colonies located nearby. If your orchard is located near natural pollinator habitat, you may receive sufficient wild pollinators to obtain significant fruit set, in which case additional bees may not be necessary. Foraging honey bees typically seek out the least competitive forage sources, so if your orchard without honey bee colonies is located near an orchard in which the grower paid for pollination services, it is likely you are “borrowing” bees from your neighbor's orchard. In that situation, bringing in managed honey bees may not make the most economic sense from your perspective, but it may make your neighbor happy!
Supply of honey bee colonies
Depending on location, avocado bloom can begin in late March/early April and last through May/June (Bender, 2013). One important factor in the availability of honey bee colonies for pollination services for avocado bloom is the number of colonies in California at the end of almond bloom. In 2020, roughly 2.4 million colonies were required to pollinate California's almond orchards, far exceeding the number of colonies that remain in California year-round. This means roughly 2 million colonies were shipped in to California to meet this demand. This number makes up approximately 88% of the total number of colonies in the U.S., so beekeepers bring colonies from as far as New York and Florida to meet these needs (Goodrich and Durant, 2020; Goodrich, 2019).
For avocado growers, this means at the very beginning of avocado bloom, there may still be a surplus of bees left in California. Beekeepers from northern states, e.g., North Dakota, South Dakota, and Montana, can't transport colonies back right away given there may still be snow on the ground and little blooming for the bees to forage on. However, as spring progresses throughout the rest of the U.S., the number of bees in California begins to decrease substantially. Looking at the U.S. Department of Agriculture (USDA) Honey Bee Colonies Report, on April 1, 2018, there were 1.1 million colonies in California and by July 1, 2018 the number of colonies was nearly half that at 590,000.
Traditionally, California beekeepers would place colonies in or near citrus orchards for honey production after almond bloom (Champetier, 2010). In addition to being good for bees (and their keepers), this practice has benefitted growers of nearby crops that require pollination services. For example, a beekeeper might place colonies for no charge in an avocado orchard that needs pollination services simply to gain access to the prime honey-producing location. However, given the surplus of colonies remaining in California after almond bloom, I suspect (notably without any direct empirical evidence) these locations are not as prime as they once were. Supporting evidence for my theory is shown in Figures 1 and 2. Figure 1 displays a fairly prominent downward trend in total honey-producing colonies in California since 1990, and over the same time period, the average amount of honey produced per colony in California has trended downward as well. If the essential inputs to honey production, i.e., floral nectar and pollen sources, were roughly equivalent over this time period, one would expect for honey production per colony to increase as the number of colonies decreases given the lower competition over floral sources. Figure 2 shows bearing citrus acreage over this time period. Citrus acreage has decreased since the late 1990s, which might partially explain lower honey production per colony in recent years. However, the decreasing trend in honey production per colony occurred even in the late 1990s when citrus acreage in California was increasing. These trends suggest that the influx of bee colonies due to almond pollination requirements have encroached on forage resources previously utilized by California beekeepers, lowering their potential for honey production. Again, I caveat the previous suggestion with the fact that I have not yet directly tested this hypothesis, so these relationships could be coincidental.
Get the whole story at: http://ceventura.ucanr.edu/Com_Ag/Subtropical/
- Author: Dana Yount
- Contributor: Kristian M Salgado
- Contributor: Emily Lovell
- Contributor: Caddie Bergren
- Contributor: Nicki Anderson
- Contributor: Shulamit Shroder
- Contributor: Samikshya Budhathoki
- Contributor: Esther Mosase
- Contributor: Valerie Perez
UC ANR Climate Smart Agriculture Educator team assisted growers to win CDFA grants that reduced greenhouse gases equivalent to removing roughly 7,000 cars off the road, supporting UC ANR's public value of building climate-resilient communities and ecosystems.
The Issue
Increasingly extreme and erratic weather patterns caused by climate change threaten crop yields and farm profits across the state. Growers must continue to adapt to climate stressors, such as increased temperatures and occurrences of drought, and can aid in reducing climate change through their farming practices.
How UC Delivers
A collaborative partnership between the Strategic Growth Council, California Department of Food and Agriculture (CDFA), and University of California Agriculture and Natural Resources (UC ANR) teamed up to support 10 Climate Smart Agriculture Community Education Specialists (CSA CES) throughout the state to provide technical assistance and outreach to promote Climate-Smart Agriculture Incentive Programs. These programs include:
- The Healthy Soils Program, which incentivizes the implementation of climate-smart agriculture practices such as cover cropping, composting, crop rotation, and mulching which reduce erosion and greenhouse gases
- The State Water Efficiency and Enhancement Program (SWEEP), which encourages farmers to install more efficient irrigation systems that decrease water consumption and greenhouse gas (GHG) emissions; and
- The Alternative Manure Management Program (AMMP), which awards funds to livestock producers who decrease their methane emissions by changing the way they manage manure.
Since establishing this partnership in 2019, the UC ANR Climate Smart Agriculture Educator team has provided hands-on assistance to over 200 farmers and ranchers through the complex application process. Collaborating with other CDFA technical providers to host workshops, field days, and events has expanded reach to a greater number of growers, over 120 of whom were able to receive funding after receiving technical assistance. UC CSA CES efforts don't stop at the outreach or application phase; educators work year-round to ensure successful implementation of climate-smart projects.
After the award process, educators assist awardees in completing grant invoicing and contract reporting requirements and connect them with vendors, industry experts, and service providers. UC CSA CES also engage in a variety of additional support activities. For example, to help establish successful cover crop adoption, one educator created a cover crop decision-making tool. A different educator started a small compost spreader rental program to assist small growers in spreading compost. Another facilitates full project management through translation services to a cooperative of Cantonese-speaking awardees.
The Impact
Through assisting awardees in the adoption of practices such as cover cropping, installing solar panels, and installing dairy manure solid separator systems, the 10 UC CSA CES have collectively supported growers in reducing 33,000 MT/CO2 per year, as measured by California Air and Resources Board (CARB) Green House Gas Emission reduction calculator (SWEEP GHG Calculator on CDFA's website), and the HSP Comet planner tool. That's equivalent to removing 7,000 cars from the road per year.
Table A provides an overview of how much GHG has reduced in counties where the UC Climate Smart Agriculture Educator team has helped farmers implement climate-smart practices. Totals for all projects are much higher.
UCCE-County Location |
Total CO2 equivalent in MT/year |
Sonoma, Mendocino, and Lake County |
314.2 |
Merced, Madera, Stanislaus |
5263.31 |
Glenn, Butte, Colusa, Tehama County |
4545.785 |
Yolo, Solano, Sacramento, San Joaquin, El Dorado, Sonoma, Colusa, Sutter |
11716.4 |
Santa Clara County |
58.85 |
Fresno County |
1353.924 |
Kern & Tulare Counties |
7060.283 |
Santa Barbara, Los Angeles, Orange, Ventura County |
630.5 |
San Diego and Riverside Counties |
300.18 |
Imperial County and Riverside County |
3689.1 |
Glenn County grower, Shannon Douglass says, “When producers have the support from the UCCE office that they already know and trust, they are more willing to implement new practices. The application process is intimidating, but with the help from UC, soil healthy practices are becoming much more widely adopted.”
Research shows that Healthy Soils Program practices such as compost application increases the amount of organic matter in soil, amongst numerous other benefits such as increasing the water and nutrient retention capacity of soils, providing a reservoir of nutrients for plants, improving aeration, improving water infiltration, reducing soil erosion, and supporting the abundance and diversity of soil organisms, which can improve plant health. Compost application is just one fundable practice farmers can implement to help reduce greenhouse gases on their operation.
Thanks to this unique partnership with CDFA, UC ANR is able to provide hands-on support to farmers statewide so that they can improve the health of their soils, reduce livestock methane emissions, and improve water use efficiency. In this way, the Climate-Smart Agriculture program contributes to UC ANR's public value of building climate-resilient communities and ecosystems.
- Author: Ben Faber
Get Ready to learn more about our fragile world
and how to deal with drought, heat, fire, winds
and climate change
https://www.drought.gov/states/California
And a lot more information on fire, water and climate change
https://ucanr.edu/News/For_the_media/Press_kits/
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Developing a nitrogen fertilizer plan for olive orchards
Elizabeth J. Fichtner, Farm Advisor, UCCE Kings and Tulare Counties
Nitrogen management plans (NMP) for California olive orchards are essential for the Irrigated Lands Regulatory Program and can increase net return. A good NMP has the potential to increase yield, improve oil quality and mitigate biotic and abiotic stresses while reducing nitrogen losses from the orchard.
Olives differ from other orchard crops in California in that they are both evergreen and alternate bearing. Individual leaves may persist on the tree for two to three years. Leaf abscission is somewhat seasonal, with most leaf drop occurring in late Spring. Rapid shoot expansion occurs on non-bearing branches during the hottest part of the summer (July-August) on ‘Manzanillo' olives in California. The fruit on bearing branches limits current season vegetative growth. Olives bear fruit on the prior year's growth, and the alternate bearing cycle is characterized by extensive vegetative growth in one year followed by reproductive growth the following year (Figure 1). With bloom occurring in late April to mid-May, fruit set can be estimated in early July, allowing for consideration of crop load while interpreting foliar nutritional analysis in late July-early August.
Critical Nitrogen Values. Foliar nitrogen content in July/August should range from approximately 1.3-1.7% to maintain adequate plant health. The symptoms of nitrogen deficiency manifest when foliar nitrogen content drops to 1.1% nitrogen. As leaves become increasingly nitrogen deficient, foliar chlorosis progresses from yellow/green to yellow. Leaf abscission is common at nitrogen levels below 0.9%. Nitrogen deficiency in olive is associated with a reduced number of flowers per inflorescence, low fruit set, and reduced yield.
Excess nitrogen (>1.7%) adversely affects oil quality. Oil with low polyphenol concentration is associated with orchards exhibiting excess nitrogen fertility. Since polyphenols are the main antioxidant in olive oil, reduced polyphenol levels are associated with reduced oxidative stability.
Nitrogen content may impact orchard susceptibility to biotic and abiotic stresses. For example, while excess nitrogen content has been associated with increased tolerance to frost prior to dormancy, in spring (post-dormancy) it is associated with sensitivity to low temperatures. High nitrogen content has also been associated with increased susceptibility to peacock spot, a foliar fungal disease on olive.
Foliar Sampling for Nitrogen Analysis. By convention, foliar nutrient analysis is conducted in late July-early August in California. Fully-expanded leaves are collected from the middle to basal region of the current year's growth at a height of about 5-8 feet from the ground. To capture a general estimate of the nitrogen status of the orchard, samples should be taken from 15-30 trees, with approximately 5-8 leaf samples collected per tree. Leaves for analysis should only be collected from non-bearing branches. Growers may find it beneficial to make note of the ON and OFF status in the historical records of each block. The orchard bearing status, combined with anticipated yield and foliar analysis will guide decisions for nitrogen applications the following year.
Distribution of nitrogen in the olive tree. Over 75% of the aboveground nitrogen in the olive tree is incorporated in the vegetative biomass (Figure 2). The twigs, secondary branches, main branches, and trunk account for approximately 33% of aboveground nitrogen (Figure 2). Twenty-three percent of the aboveground nitrogen is harbored in the fruit, with the majority in the pulp (19%) (Figure 2). Fruit is only an important nitrogen sink during the initial phase of growth. As fruit size increases, the N concentration decreases due to dilution.
Estimation of nitrogen removed from the orchard. The easiest component of orchard nitrogen loss to estimate is the nitrogen in the harvested fruit. A ton of harvested olives removes approximately 6-8 lbs of nitrogen from the orchard. The quantity of nitrogen in the fruit varies slightly between olive varieties (Table 1). Growers can use the Fruit Removal Nutrient Calculator for Olive on the California State University, Chico (CSU Chico) website to gain estimates of N removal by the three oil varieties (Arbequina, Arbosana, and Koroneiki), and the Manzanillo table olive. This tool was developed by Dr. Richard Rosecrance (Professor, CSU Chico) and Bill Krueger (Farm Advisor, UCCE). To access the Fruit Removal Nutrient Calculator for Olive, visit the following URL:
http://rrosecrance.yourweb.csuchico.edu/Model/OliveCalculator/OliveCalculator.html
Pruning may generate a second component of nitrogen loss from orchards. The best practice to mitigate nitrogen loss from pruning is to reincorporate the pruned material into the orchard floor by flail mowing. The nitrogen in this organic material will gradually become available to the trees through mineralization.
In mature orchards, the wood removed by annually pruning is approximately equal to the annual vegetative growth. Consequently, the input and removal of nitrogen in vegetative growth is cyclic and almost equal in mature orchards. In young orchards, nitrogen inputs are utilized to support vegetative growth and little nitrogen is removed from the orchard in prunings or crop. During this time nitrogen must be supplied to meet the demand to support vegetative growth. It is estimated that approximately 2.5 lbs nitrogen is required to produce 1,000 lbs. fresh weight of tree growth.
Nitrogen Use Efficiency. Not all the nitrogen supplied to the orchard from fertilizer and other inputs (ie. organic matter, irrigation water) is utilized for tree growth and crop production. A fraction of nitrogen is lost from the orchard ecosystem through processes such as runoff, leaching, and denitrification. Efficiency varies among orchards, with some orchard systems exhibiting higher nitrogen utilization rates than others. The efficiency generally varies from 60% - 90%. Higher values denote more efficient use of nitrogen inputs. To estimate the amount of nitrogen to supply an orchard, the demand is divided by the estimated efficiency. For example, if nitrogen demand is 50 lbs. per acre and efficiency is estimated at 0.8, then 62.5 lbs. of nitrogen per acre should be applied.
Summary. Nitrogen management plans are site-specific and designed to meet orchard and crop demand while reducing environmental losses. Nitrogen utilization is never 100% efficient. Nitrogen use efficiency can be maximized by minimizing losses from irrigation and fertilization practices while utilizing foliar analysis and knowledge of alternate bearing status to fine-tune applications.
Select References:
Fernández-Escobar, et al. 2011. Scientia Horticulturae 127:452–454.
Hartman, H.T. 1958. Cal Ag. Pgs 6-10.
Rodrigues, M.A. et al. 2012. Scientia Horticulturae 142:205-211.