- Author: Ben Faber
A $1.5 million emergency grant is enabling UC Riverside scientists to find plants impervious to a disease threatening America's citrus fruit supply.
Citrus Greening Disease — also known as Huanglongbing, or HLB — results in fruit that is bitter and worthless. It has crippled Florida's citrus industry and has already been detected in California, which grows 80% of America's fresh citrus. An estimated 267,000 acres of Golden State oranges, lemons, grapefruits, and mandarins are at stake.
For these reasons, the National Institute of Food and Agriculture is supporting scientists at UCR, the University of Florida, and the U.S. Department of Agriculture's Agricultural Research Service in their search for plants with natural tolerance to HLB.
“If you find a disease affecting your crops, a good first step is to look for plants that are able to grow and produce despite infection,” said UCR geneticist Danelle Seymour. “Then you can start to identify the genetic basis of the disease tolerance and make sure the next generation of plants includes these genes.”
Following this recipe, Seymour and UCR plant pathologist Philippe Rolshausen will examine a set of 350 citrus hybrids developed and grown by project collaborators in Florida. All trees in the set are already infected with HLB, yet they live longer, are healthier, and yield more fruit than their infected relatives.
While there are a number of projects searching for different solutions to the threat of HLB, this project is different because the plants being tested were all grown in an environment endemic to the disease. Additionally, the number of plants they're able to test is unusually large.
“The environment in which these plants were grown means we can be confident that these rootstocks will enhance tree health and yield in HLB-affected areas,” Seymour said. “Also, because our data set is so large, we've got the opportunity to identify plants with levels of tolerance that exceed current commercial varieties.”
In addition to searching for parts of the hearty hybrids' genomes responsible for their tolerance to HLB, scientists will also be checking for plants that have resistance to other pathogens that are already in California.
Citrus in the state is also threatened by nematodes that chew up roots, preventing plants from taking up nutrients, and by phytophthora, a type of water mold that causes rotting roots.
By searching not only for a solution to the looming threat of HLB but also to problems that have already taken root in California, scientists are hoping to ensure that citrus won't need to be imported from HLB-free countries and costs stay low for both local growers and consumers.
“This way, we're making sure the next generation of rootstocks will include the right genes and that we're being as efficient as possible in our breeding practices,” Seymour said.
ACP nymph image by Sam Droege, USGS
- Author: Ben Faber
Avocado Café is intended to be a meeting of interested avocado growers from California and elsewhere with an open discussion for ideas and inputs. Our organizing committee primarily consists of California growers but also has extension personnel and international members as well. Although we cover the “how to” aspects of avocado farming we are most focused on introducing new concepts and ideas to the avocado community to stimulate further discussion and innovation. We draw upon local, national and international speakers for these sessions. The sessions are recorded and posted to all interested parties on www.avocadosource.com.
Avocado Café
February 18, 2022
8:00 – 10:00 a.m. PST
Avocado productivity:
How the interplay of light and vegetative vigor influences yield
Speakers:
Rodrigo Iturrieta, University of California, Riverside
How shoot growth influences fruiting and light distribution
Gerardo Adunate, Avocado Consultant, Chile
Optimizing pruning strategies to increase light and enhance fruit production
These sessions are open to all. Register for this virtual meeting by emailing cafeavos@gmail.com
- Author: Ben Faber
The calls have come in. Citrus Dry Root Rot has struck. It's not supposed to happen this time of year. We've gone from this beautiful, rainy December to a mild winter mid-80s on some days. But, we had a fierce Santa Ana mid-January that knocked down street trees and caused other damage. And that's the cause. The devil wind. It's shocking how fast the citrus trees go from green to a lifeless brown.
BOOM!
The parting words of my predecessor Nick Sakovich (happily living in Hawaii) were: DRR hits trees between 1-15 years of age, less-well managed trees, trees that have been injured (gophers, weed whips, discing, fertilizer burn, etc.), in the presence of the Fusarium fungus, and it always happens on the first hot day of spring. A nice mild, or even cool winter, and then there is a sudden water demand by the tree on a hot day and BOOM, the tree's leaves turn brown in a weekend.
Dry Root Rot has menaced growers in Ventura County for many years. In the ‘50's and ‘60's it seemed most prevalent on older orange trees. A few years after the wet winter of 1968-69, dry root rot became an increasing problem among citrus trees of all ages. At that time, most of the damaged trees were on sweet rootstock (susceptible to Phytophthora), and growing in fine-textured soils or soils with poor drainage. A few years after another wet winter/spring (of 1983), dry root rot again reared its ugly head, but this time predominately on young lemons.
The disease is caused by the fungus, Fusarium solani. Fusarium in citrus clogs the xylem which carries water to the leaves. When damage is done to the xylem, the ability to carry water is reduced. When a lot of damage is done, that's when you get that BOOM.
The damage occurs at the base of the trunk. The bark has been cut away to show the affected wood beneath
This fungus is most likely present in all citrus soils in California. It is a weak pathogen in that by itself it will not attack a healthy tree. However, experiments conducted in the early 1980's by Dr. Gary Bender, showed that when seedlings were girdled, root invasion occurred. In the field, the fungus can infect trees once gophers have girdled the roots or crown. A Phytophthora infection will also predispose trees to Fusarium, as will asphyxiation. Therefore, the mere presence of the fungus in the orchard soil will not lead to the disease.
So we call it a disease, but it's really a complex of circumstances that need to be present. It has to be a wound, Fusarium and the weather. We forget that wind is a greater drain on a tree's water needs than heat is actually. Same for humans, you got out on a windy day, and you come home and the first thing you do is drink some water. That's the way food is freeze-dried.
And that's the stress we had this year, and BOOM!
There's not a whole lot that can be done after this happens. The way it is managed is through avoiding wounds and making sure that when stressful conditions of wind and heat are forecast, that the tree is well supplied with water.
Nick was mainly right. Dry Root Rot mainly happens with the first hot day of spring, but it can happen anytime a wounded, infected tree goes under water stress. And it can happen to older trees, too.
There's more to this story. Read more about this infuriating disease complex at the UC Integrated Pest Management website - https://www2.ipm.ucanr.edu/agriculture/citrus/Dry-Root-Rot/
And listen to Dr. Akif Eskalen's Dry Root Rot story at "What Are the UC Ag Experts Talking About?"
https://www.youtube.com/watch?v=K2fyBcC1HXk
- Author: Ben Faber
Upcoming California Avocado Disease Management Webinar
The California Avocado Society, California Avocado Commission and UC Cooperative Extension are hosting a free online Grower Webinar: Avocado Disease Management session on Wednesday, February 16 from 9:00 a.m. – 11:00 a.m.
The webinar is designed to provide growers and grove managers with information concerning management strategies for diseases that California avocado trees are prone to. The online seminar will cover:
- Approaches to combating avocado root rot, including pesticide management
- The availability of a new chemical to manage Phytophthora
- Other chemical and horticultural practices related to disease management in California avocado groves
The presenters include Dr. Ben Faber, Crops Advisor for the UC Cooperative Extension, and Dakota Camino, PCA with Syngenta.
- Author: Ben Faber
A Great Friend and Farmer Has Passed
It was announced recently that James Lloyd-Butler passed away on January 25. He was a great gentleman who loved learning, had a great love of family and was one of the best, if not the best farmers in Ventura County. He contributed significantly to the community in many ways, especially to share his love of agriculture. He was always ready to receive visitors to show how agriculture could be performed in harmony with the land. In 2018, he was recognized for his contribution to the avocado world with the following dedication from the California Avocado Society. I learned a lot from him. I, and many others, will miss him.
California Avocado Society
Award of Merit
To
Jim Lloyd-Butler
Our 2018 Award of Honor this year goes to a “first class person”, a “gracious host” and a “dream to work with”. Who is this gentleman? James Lloyd-Butler
Born here in 1925 and grew up on Rancho Santa Clara del Norte, which is one of the Mexican land grants in the Santa Clara Valley, the others being Rancho Santa Paula y Saticoy, Sespe, Olivas and Camulos. This was a farm of mainly walnuts and barley, some of it leased out to others for farming. His father managed the farm. He worked on the farm in the summers and remembers harvesting Valencias for sale to C&H Market at 10 cents a dozen. Lemons were only planted in the 1930's. There were only a few avocado trees at the time, 5 having been donated by Louie the Ranch Foreman in the name of the 5 siblings growing up there. Jim went off to Oxnard High School, got embroiled in the navy, stationed in Saipan in 1945. Came back and did 2 years of college at St. Mary's in Moraga, then two years at Cal Poly San Dimas, Voorhis unit where he also attended some lectures at UC Riverside.
Then off to make his fortune, he worked for Jack Broome at Rancho Guadalasca, another Mexican land grant. There he was superintendent of row crops – sugar beets, peppers and canning tomatoes – from 1955 – 63. And he got married to Cynthia Marsh and soon there were two kids, Camilla and Tom. Fruitful years for Jim.
Then he stretched his legs with a bit of adventure into real estate, but soon went back to ranch management and then from 1970 -82 he worked agriculture through the Bank of A. Levy. The family farm was managed by Hoffman, Vance and Worthington with the supervision of his dad. At the time there were 3 ac of Zutano, 3 ac of Bacon and 6 ac of that new variety called Hass.
With the death of his father, he took over the ranch management. At the time there were still only a few avocados, mainly lemons. From the 1980's to the present the avocado acreage expanded from 20 to 110 acres, along with a similar amount of lemons. Now the avocados are a mix of Hass, GEM, Lamb Hass, Carmen, and SirPrize and is he ever a believer in pollinizers – Walter Hole, Zutano, Ettinger and Bacon. He's done high density and has been seriously pruning since 1995. He's worked with different rootstocks and has been a serious collaborator with the university, working with Mary Lu Arpaia, Mark Hoddle, Joe Morse, John Menge and others.
He has always surrounded himself with wise guys, people he consults. George Powers, the manager of the farm before he was born, Roger Edwards from Limoneira, Jack Broome of Oxnard, Bud Lee and Bob Burns from UC Coop Extension, Darrel Nelson, Roger Essick.
One of the worst decisions was to plant litchi and longans at my recommendation. They never fruited here.
Gordon Frankie, the UC Berkeley Bee Biologist, who has done work here, writes:
He has been a very generous person who has greatly helped us in researching the visitors to avocado flowers. He has shown considerable interest with all of our findings, and has always offered help from his workers for all the many ideas we have explored at his ranch. He also shows curiosity and a willingness to go beyond most growers in exploring the ways that we could try new ideas, for example, expanding the bee gardens to encourage more flower visitors.
I'd like you to join me in recognizing the wonderful works that Jim has made to our community.
The Pollination/Beneficial Insect Garden that Jim helped build.