- (Public Value) UCANR: Promoting economic prosperity in California
- Author: Ben Faber
With little rain this winter and the erratic weather patterns of wind and heat, avocado is going to be especially prone to salt damage. And the flowering period is one of the most sensitive. Flowers are competing with leaves that have been hanging on for a year and have been salt stressed by a year's worth of irrigation salts. A good understanding of how salt moves and is leached it important to get through til next winter when there will hopefully be sufficient rain again to naturally leach the soil.
Water moves in a wetting front. When irrigation water hits the soil, it moves down with the pull of gravity and to the side according to the pull of soil particles (more lateral with more clay). Soil is a jumble of different sized soil particles, from clay to silt to sand sizes and then often intermixed with stones of different sizes from gravels to boulder. The different textures determine how water moves. It moves fastest through coarse textures and slowest through finer ones – the clays, the ones with the smallest pores. But soils are a jumble of particle sizes and pores.
Water first moves down the larger pores and then it slowly moves through the smaller ones. As water moves through the soil, it carries salts that have accumulated in the soil. At the wetting front is where the salt accumulates. As the water moves through the larger pores, salts migrate/diffuse from the small pores to the larger ones. This diffusion takes a bit of time, so typically the small pores have a larger salt concentration than the larger ones.
So an initial application of water will carry the salts from these large pores and if the irrigator were to stop in mid-application, it allows time for the salts to move out of the small pores into the larger ones. Then when the irrigation recommences, it will carry more of the salts out of the wetted area – the root zone. This technique is called “bumping” where an irrigation is stopped and then restarted in order to improve not only leaching, but also reduce runoff.
This principle also is at play when there are two or more sources of water quality. Soil salinity can be no lower than the irrigation water that is applied. Then as the soil, water is removed through plant absorption or evaporation, the salinity increases. The soil salinity can easily be two to three times higher than the irrigation water.
If there are two sources of water, the initial application can be with the poorer quality water, and once that has reduced the soil salinity, then the better water quality can be applied which will then bring the soil salinity closer to that of the better quality water. By doing this two part leaching, the amount applied of the better quality water can be significantly reduced. This is a type of “bumping” to improve leaching.
Watch this U-Tube video on how water moves through soil, thanks to the work at Walla Walla Community College.
https://www.youtube.com/watch?feature=player_detailpage&v=J729VzBeI_g
Thank you Walla Walla Community College for the video
- Author: Ben Faber
Citrus Nematode (Tylenchulus semipenetrans)has been considered a problem in some areas and some Citrus growing conditions. Here's an example from Cole Crops where natural biological control is working and most likely would work in Citrus. Why not, they all start with "C". But just need to create the right conditions for this to happen.
Over the past 30 years, the use of soil fumigants and nematicides used to protect cole crops, such as broccoli and Brussel sprouts, against cyst nematode pathogens in coastal California fields has decreased dramatically. A survey of field samples in 2016 indicated the nematode population has also decreased, suggesting the existence of a natural cyst nematode controlling process in these fields.
Thanks to California's pesticide-use reporting program, nematologists have been able to follow the amounts of fumigants and nematicides used to control cyst nematodes over the past three decades. "Application of these pesticides steadily declined until they were completely eliminated in 2014 while, for example, broccoli yields continued to increase each year," said Ole Becker, a scientist with the Department of Nematology at the University of California.
In a study of 152 fields, Borneman, Becker and colleagues detected cyst nematodes in about 38% of them. Only a few of these fields had enough nematodes to potentially damage the crops. This showed that growers had likely reduced their usage of nematicides because of a natural decline in the nematode populations.
To identify the cause of this natural decline, Borneman, Becker and colleagues used cyst nematodes as a bait and found that a diverse population of fungi were likely killing the nematodes. The most abundant genus was Hyalorbilia, which contains species previously described as effective parasites of cyst and root-knot nematodes.
"The results from our baiting analysis combined with advanced molecular tools gave us a detailed depiction of the possible nematode-parasitizing fungi in these soils, which then provided a plausible explanation for this dramatic decrease in pesticide use," said Borneman.
Their research demonstrates the usefulness of monitoring plant-parasitic nematode density before using nematicides and increases the awareness of beneficial fungi in crop protection. These fungi might be considered as possible biological control agents for nematodes.
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To learn more, read "Detection of Nematophagous Fungi from Heterodera schachtii Females Using a Baiting Experiment with Soils Cropped to Brassica Species from California's Central Coast" published in the January issue of PhytoFrontiers.
Hschachtii on cabbage roots held by Ole Becker
Author: Jules Bernstein, UCR,Senior Public Information Officer
New research affirms a unique peptide found in an Australian plant can destroy the No. 1 killer of citrus trees worldwide and help prevent infection.
Huanglongbing, HLB, or citrus greening has multiple names, but one ultimate result: bitter and worthless citrus fruits. It has wiped out citrus orchards across the globe, causing billions in annual production losses.
All commercially important citrus varieties are susceptible to it, and there is no effective tool to treat HLB-positive trees, or to prevent new infections.
However, new UC Riverside research shows that a naturally occurring peptide found in HLB-tolerant citrus relatives, such as Australian finger lime, can not only kill the bacteria that causes the disease, it can also activate the plant's own immune system to inhibit new HLB infection. Few treatments can do both.
Research demonstrating the effectiveness of the peptide in greenhouse experiments has just been published in the Proceedings of the National Academy of Sciences.
The disease is caused by a bacterium called CLas that is transmitted to trees by a flying insect. One of the most effective ways to treat it may be through the use of this antimicrobial peptide found in Australian finger lime, a fruit that is a close relative of citrus plants.
"The peptide's corkscrew-like helix structure can quickly puncture the bacterium, causing it to leak fluid and die within half an hour, much faster than antibiotics," explained Hailing Jin, the UCR geneticist who led the research.
When the research team injected the peptide into plants already sick with HLB, the plants survived and grew healthy new shoots. Infected plants that went untreated became sicker and some eventually died.
Arrows point to areas of fluid leakage from the bacterial cell after treatment with the antimicrobial peptide. (Hailing Jin/UCR)
"The treated trees had very low bacteria counts, and one had no detectable bacteria anymore," Jin said. "This shows the peptide can rescue infected plants, which is important as so many trees are already positive."
The team also tested applying the peptide by spraying it. For this experiment, researchers took healthy sweet orange trees and infected them with HLB-positive citrus psyllids -- the insect that transmits CLas.
After spraying at regular intervals, only three of 10 treated trees tested positive for the disease, and none of them died. By comparison, nine of 10 untreated trees became positive, and four of them died.
In addition to its efficacy against the bacterium, the stable anti-microbial peptide, or SAMP, offers a number of benefits over current control methods. For one, as the name implies, it remains stable and active even when used in 130-degree heat, unlike most antibiotic sprays that are heat sensitive -- an important attribute for citrus orchards in hot climates like Florida and parts of California.
In addition, the peptide is much safer for the environment than other synthetic treatments. "Because it's in the finger lime fruit, people have eaten this peptide for hundreds of years," Jin said.
Researchers also identified that one half of the peptide's helix structure is responsible for most of its antimicrobial activity. Since it is only necessary to synthesize half the peptide, this is likely to reduce the cost of large-scale manufacturing.
The SAMP technology has already been licensed by Invaio Sciences, whose proprietary injection technology will further enhance the treatment.
Following the successful greenhouse experiments, the researchers have started field tests of the peptides in Florida. They are also studying whether the peptide can inhibit diseases caused by the same family of bacteria that affect other crops, such as potato and tomato.
"The potential for this discovery to solve such devastating problems with our food supply is extremely exciting," Jin said.
​Untreated citrus plants on the left, as compared to treated ones on the right. (Hailing Jin/UCR)
- Author: Petr Kosina
Recording of the January 2021 webinar on Current Challenges for Avocado Weed Management by Sonia Rios is now available on YouTube playlist - https://youtu.be/7zFFeJWGvyE
Upcoming UC Ag Experts Talk webinars:
For February we have scheduled presentation about Citrus Mites (Wednesday February 17 at 3 p.m.). David Haviland, UCCE Farm Advisor will discuss integrated pest management for five different species of mites that cause economic damage to citrus, including proper identification, monitoring, and tools for management. Biological control will also be discussed, including the use of predatory mites. One DPR CE unit (other) and one CCA CE unit (IPM) were requested. Register at https://ucanr.zoom.us/webinar/register/WN_ZF3LS0vNQTS_flTXTKayuA
In March, Dr. Jhalendra Rijal, UCCE Area IPM Advisor, will discuss Invasive brown marmorated stink bug (BMSB) and other hemipteran bug pests of almonds (Wednesday March 24 at 3 p.m.). Jhalendra will talk about the identification, biology and feeding nature of BMSB other native stink bugs and leaffooted bugs that may be present in an almond orchard, and provide a comprehensive IPM strategy to manage these multiple hemipteran pests in almond orchards. One DPR CE unit (other) and one CCA CE unit (IPM) were requested. Register at https://ucanr.zoom.us/webinar/register/WN_yJp9VDQzSCe-cnihKD1m4w
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Other virtual events that might be of your interest:
California Avocado Society seminar Series 2021:
The Efficacy of Gibberellic Acid in Improved Fruit Set (by Dr. Tim Spann) and an Update on New Avocado Varieties (by Dr. Mary Lu Arpaia) - February 17, 9 a.m.–11 a.m. [No CEUs] Register at https://ucanr.zoom.us/webinar/register/WN_i0oPDqyiT_2noK4GYGBiwQ
Science for Citrus Health spring webinar series:
Emerging Technologies to Manage Asian Citrus (ACP) and Huanglongbing (HLB) – February 24, 10 a.m.–12 p.m.
- Therapeutic molecule evaluation and field delivery pipeline for solutions to HLB (Dr. Michelle Heck, USDA ARS)
- Viruses of ACP and approaches to use them as a pest management tool (Dr. Bryce Falk, Professor Plant Pathology, UC Davis)
- Managing ACP with pesticidal proteins derived from bacteria (Dr. Bryony Bonning, Professor Insect Pathology, University of Florida)
- Q&A and panel discussion
1.5 DPR and CCA CEUs were requested. Register at https://ucanr.zoom.us/webinar/register/WN_i6s_wxvsQ-K1dXwgp5_Emw
Management of Asian Citrus Psyllid (ACP) and Huanglongbing (HLB) in the field – March 11, 10 a.m.–12 p.m.
- Relation of ACP density and tree stress: what is the threshold to take control measures? (Dr. Lukasz Stelinski, Professor, Entomology and Nematology, University of Florida)
- Biological control of ACP using predators and parasitoids (Dr. Jawwad Qureshi, Assistant Professor, Entomology and Nematology, University of Florida)
- Importance of citrus phenology-based sprays for ACP control and Implementation of ACP area-wide management in Texas (Dr. Mamoudou Sétamou, Professor, Citrus Entomology, Texas A&M University)
- Q&A and panel discussion
1.5 DPR and CCA CEUs were requested. Register at https://ucanr.zoom.us/webinar/register/WN_I7KPgo3STaqwKwJXJQ9Fkw
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Recordings of the past webinars are available on UC IPM YouTube channel at https://www.youtube.com/playlist?list=PLo3rG4iqv4gHBV3YA6w4wkBufwh7GBjrX
UC Ag Experts Talk team
How can various cultivars influence
the history of a crop?
Not many of us see Model T cars on the road today. This 1920's era car made car travel accessible for the middle class, but its last production was in 1927. Yet, some of the engineering that went into the Model T still has an impact on today's cars.
In the same way, older varieties of crops, now much-improved, may today occupy very few acres of land. Where they once were the major variety of the day, their impact is on the history – and genetics – of their specie.
A type of wheat called Madsen, is one of those varieties not widely produced today. But its impact on today's wheat, and future generations, is undeniable. Released in 1988 for production in the Pacific Northwest, Madsen is a soft white winter wheat. It has a high yield potential. But, newer, higher producing cultivars are now more popular, but that doesn't negate the importance Madsen has in the success of today's wheat cultivars.
Madsen's legacy has gone far beyond commercial production. Madsen has been the parent of over 45 released cultivars, many of which were the lines that replaced it in commercial production. It is used as a parent mainly because of the excellent disease resistance it has to common diseases of the PNW. Madsen has also been used in research projects to identify disease resistance genes. In some cases, Madsen was found to be carrying resistance genes the breeder was not aware of but were discovered later in research or field screenings.
A plant breeder's goal is to release cultivars that are commercially economical and environmentally sustainable. The premise is that new cultivars released are superior to those that are currently available. Through multiple years of testing in small-plot trials, released cultivars and new breeding lines are evaluated for many agronomic traits such as heading date, plant height, yield potential, etc. Furthermore, new breeding lines are subjected to different biotic stress conditions to evaluate pest and disease resistance traits. They may even be subjected to different abiotic stress conditions, either under field or controlled conditions, such as cold temperatures, drought, or low pH soils. After multiple years of testing, breeding lines that have better performance than currently grown cultivars are released for commercial production. Although plant breeders have multiple years of data supporting the performance of the new cultivar, there is no true indicator of how it will perform as a new cultivar until it is released and growers cultivate it on large acreage under commercial production systems.
During its development, Madsen showed very effective resistance to Pacific Northwest races of the stripe rust fungus and to leaf and stem rust. This disease resistance is important, as fungal diseases spread easily and reduce yields. In fact, Madsen was originally developed to be resistant to a different disease, eyespot foot rot.
Commercial Production
Once Madsen was released as a cultivar, it became widely grown in only a few years. At one time, 20% of the wheat produced in the Pacific Northwest was Madsen. It remained the most widely grown cultivar in the PNW for almost 13 years. Madsen has also been blended and planted with other cultivars in the same field to manage pests because of its excellent disease resistance. This production history has been an impressive 30-year life of a cultivar!
Breeding value
Approximately 45 cultivars have been released in the Pacific Northwest containing Madsen as a direct parent or somewhere within the pedigree. Six of these have been the leading cultivars in either Oregon or Washington for multiple years based on planted hectares.
Agronomic value
If you have ever driven by a field of beautiful wheat and see some of it laying on the ground (versus upright), that is called lodging. Lodging can hurt the value of wheat. Madsen has a lower rate of lodging than other wheats, which could be because its stems are strong. In addition, its resistance to fungal diseases may also help.
Consumer value
No cultivar of crop will remain on the market long if its end-users do not buy it. In addition to how well Madsen performs in the field, it also has excellent baking properties.
Answered by Arron Carter, Washington State University
Fun fact: did you know that many cultivars are named after people? Madsen was named in honor of Dr. Louis L. Madsen, Dean of the College of Agricultural, Human, and Natural Resource Sciences at Washington State University from 1965 to 1973. Dr. Madsen was an effective advocate of wheat research at the university, and a strong supporter of the collaboration between the USDA units and the College on campus.
Dr. Carter recently published a paper about the lineage of Madsen in Journal of Plant Registrations.
About us: This blog is sponsored and written by members of the American Society of Agronomy and Crop Science Society of America. Our members are researchers and trained, certified, professionals in the areas of growing our world's food supply while protecting our environment. We work at universities, government research facilities, and private businesses across the United States and the world.
Images of avocado forerunners of 'Hass' variety
