- Author: Michael Hsu
Wet winter, El Niño create favorable conditions for aerial Phytophthora pathogen
With heavy rains in the forecast amid strengthening El Niño conditions, almond growers should be on the lookout for a rare disease that can cause severe damage to their orchards, according to Florent Trouillas, a University of California Cooperative Extension specialist in fruit and nut pathology.
Phytophthora, soilborne microorganisms dubbed “water molds” because of their dependence on water, typically cause root and crown rot at the base of trees. But a few aerial Phytophthora can travel upwards and infect the higher parts of the tree. One species – Phytophthora syringae – is drawing special attention due to an unprecedented outbreak last winter, fueled by the atmospheric rivers that lashed California.
“It was found statewide – meaning in every almond-producing county – and disease incidence in orchards ranged from 10% of the trees infected to 75%,” said Trouillas, a UC Davis plant pathologist whose lab is based at UC Agriculture and Natural Resources' Kearney Agricultural Research and Extension Center in Parlier.
Trouillas and his colleagues, UC Davis graduate student Alejandro Hernandez and UC Riverside plant pathology professor Jim Adaskaveg, recently published a detailed online article describing the pathogen, which can infect a range of crops but mainly impacts almonds in California.
Although it doesn't kill the tree, the disease causes branch dieback that requires significant additional work and expense for almond growers. In 2022, almonds were the state's fourth-highest valued commodity, at $3.52 billion.
During last year's aerial Phytophthora outbreak, researchers also observed a new and troubling phenomenon: P. syringae, historically known to attack the cuts caused by pruning, was directly infecting the young shoots on almond trees – without any wounds.
“This was really the first time we had seen widespread evidence of infection on the twigs,” Trouillas said.
Although generally rare, outbreaks of P. syringae have been traditionally associated with wet El Niño years, according to Trouillas – and recent and persistent rain across the state should have growers on high alert.
Prune in dry weather, monitor, mitigate if necessary
While almond growers tend to prune during the downtime of winter, they should keep an eye on the forecast and aim for a 10- to 14-day window of dry weather to perform those tasks, whether training young trees or maintaining the established ones.
“If growers were to prune around a rain event – before, during or shortly after – this increases the likelihood of infection because this pathogen moves around with water,” Trouillas explained.
Researchers speculate that P. syringae, normally found in the soil, gets carried into the upper parts of a tree through strong winds and heavy rain. Alternatively, harvest processes like shaking and sweeping also produce air movements that may blow the microorganism into the canopy, where it waits for a favorable wet environment. The pathogen then attacks the wounds or young shoots, producing characteristic cankers and gumming.
The patterns and colors of the gum balls are keys to diagnosing an infection of this particular aerial Phytophthora. Starting around bloom time (mid-February), growers should monitor pruning wounds and young shoots on their trees, especially in the canopy, for signs of the disease.
The unique coloration of the gum balls – ranging from gold and amber to dark burgundy to bright red (see photos) – generally indicates P. syringae infection. But growers are urged to contact their local Cooperative Extension advisor for confirmation.
“It is super critical for growers that, whenever they see gumming, not to assume that it is this aerial phytophthora, because there are many other diseases that can cause gumming on the tree,” Trouillas said.
If the diagnosis is confirmed, growers may apply a compound that can mitigate the infection. The plant pathologists' recent writeup describes several curative treatment options, as well as a preventive measure that reduces the amount of pathogen in the soil and thus the likelihood of infection.
For more information on the pathogen's history and biology, as well as various options for disease management, visit the article on Sacramento Valley Orchard Source: https://www.sacvalleyorchards.com/almonds/trunk-soil-diseases/aerial-phytophthora-outbreaks-in-wet-years.
/h3>/h3>- Author: Lynn M. Sosnoskie
University of California Small Grains - Alfalfa/Forages Field Day
Wednesday, May 15, 2019
UC Davis Department of Plant Sciences Field Headquarters
2400 Hutchison Dr., Davis, CA 95616, Davis, CA
8:00-4:30 Includes Lunch
CEUs: TBD
The annual UC Small Grains/Alfalfa-Forages Field Day will be held on May 15th at the University of California, Davis Department of Plant Sciences Field Headquarters on Hutchinson Road (west of Highway 113) from 8AM – 4:30PM.
The event showcases UC efforts in breeding and agronomic research related to small grains, alfalfa and forage crops and is one of the longest running field days in the state. The small grains portion will take place from 8 to noon and the alfalfa/forages section will take place between 12:40 and 4:30. A barbecue lunch will be provided.
Agenda:
7:30 Registration (no charge)
8:00 Start of Small Grains Program
8:00 Welcome and Opening Remarks
8:35 Malting Barley & Oat Breeding: Alicia del Blanco, UC Davis
8:45 Barley Breeding for Food, Feed and Forage: Allison Krill-Brown, UC Davis
9:00 New Wheat Varieties: Oswaldo Chicaiza, UC Davis
9:15 Breeding Triticales for Bread and Forage: Josh Hegarty, UC Davis
9:25 Increasing Grain Size and Number: Alejandra Alvarez, UC Davis
9:35 A New Gene Controlling Number of Grains Per Spike: Saarah Kuzay, UC Davis
9:40 Balancing Source and Sink to Increase Yield: Jorge Dubcovsky, UC Davis
10:00 Herbicide Programs for Barley and Wheat: small grain herbicides and maximizing efficacy for control: Lynn Sosnoski, UC Cooperative Extension
10:20 Italian Ryegrass: Updates on Cultivation vs Herbicide Trials: resistance and methods for control: Konrad Mathesius, UC Cooperative Extension
10:30 Warm-season legume cover crop between winter small grains: Michelle Leinfelder-Miles, UC Cooperative Extension (This project was supported by the California Climate Investments program.)
10:45 Using Nitrogen Rich Reference Zones to Guide Wheat Topdress Decisions in the Sacramento Valley: Sarah Light, UC Cooperative Extension
10:55 Yield and Protein Stability for Wheat and Triticale Varieties Grown under N and Terminal Drought Stress: Mark Lundy, UC Cooperative Extension
11:05 Updates on UC Statewide Small Grain Trials: Seasonal conditions, pests and diseases, nitrogen management, and extension efforts: Mark Lundy, UC Cooperative Extension
11:15 Comments from breeders with entries in UC Statewide Small Grain Trials
11:30 UC Statewide Small Grain Trial Observations
11:50 Return for lunch
12:00 BARBEQUE LUNCH – Sponsored by CCIA – Many thanks to the staff at CCIA!
12:40 Start of Alfalfa and Forage Portion
12:40 Welcome and Introductions—Dan Putnam, UCCE/UCD Alfalfa Specialist
12:50 Managing Alfalfa in a Wet Year- What are the Diseases?-How to Help your Fields Recover? Rachael Long, UCCE Farm Advisor, Yolo County, Woodland, CA
1:05 IPM and Managing for Weevil Resistance in Alfalfa – Ian Grettenberger, Entomology Specialist, UC Davis, CA
1:20 Evaluation of N Stabilizers in Corn –Michelle Leinfelder Miles, UCCE Farm Advisor, Delta Region.
1:35 Forage Sorghum as a Summer Option: Controlling Sugarcane Aphid in Sorghum/ Sudangrass—Nick Clark, UCCE Farm Advisor, Kings/Fresno/Tulare Counties
1:50 Innovations in Overhead Irrigation – How that might improve Water Use Efficiency—Isaya Kisseka, UC Davis Professor, Irrigation Technology
2:10 Fun with Drones –Detecting Pest and Diagnosing Problems with Aerial Photography—Umair Gull, UC Davis Graduate Student, Plant Sciences.
2:25 Controlling Difficult Weeds in Alfalfa—Lynn Sosnoskie, UCCE Farm Advisor, Merced County.
2:50 Alternative Crops Research—Kura Clover, Switchgrass, Hemp—Dan Putnam, UC Davis
3:05 Reduced Lignin Alfalfa Varieties and Interactions with Harvest Scheduling—Brenda Perez, Graduate Student UC Davis
3:20 Analyzing Alfalfa Varieties for Pest Resistance (Nematodes, Insects, Diseases) and other characteristics—Dan Putnam, UC Davis
3:35 Alfalfa and Tall Fescue Breeding Programs at UC Davis –Charlie Brummer and students, UC Davis.
3:50 Test your Weed ID IQ: Weed Identification—Brad Hanson, UC Davis
4:15 Return to Headquarters
UCDavisFieldDay 5 15 19
- Author: Lynn M. Sosnoskie
There are several meetings featuring the research of UC ANR Staff coming up this month (August 2018). Directions to sites can be obtained through the UCCE Merced Agronomy and Weed Science Upcoming Events web page: http://ucanr.edu/sites/agronomyweedscience/Upcoming_Events/
1. West Side Pest Management Update
This meeting will cover a variety of topics including vegetable insect and disease management, the biology and ecology of field bindweed, and the management of field bindweed in agronomic and specialty crops.
Date: August 15, 2018
Time: 8:00 AM - 12:00 PM
Location: UC Westside Research and Extension Center
Event Schedule:
8:30 Welcome and introduction Tom Turini, UCCE Advisor Fresno
8:35 Recent research on vegetable insect and disease management Tom Turini
8:55 Field bindweed biology and ecology Lynn Sosnoskie, UCCE Advisor Merced/Madera
9:15 Bindweed management in annual systems Scott Stoddard, UCCE Advisor Merced/Madera
9:35 Bindweed management in perennial crops Kurt Hembree, UCCE Advisor Fresno
9:55 Bindweed control discussion
10:25 Break
10:40 Recent research on Fusarium diseases of tomato Cassandra Swett, UC Davis Department of Plant Pathology
11:10 Resistance breaking strains of TSWV and Beet curly top virus research Robert Gilbertson, UC Davis Department of Plant Pathology
11:45 Adjourn
2. Warm Season Cover Crops Field Day
Warm season cover crops are an underused tool in California agriculture. Their use can “add value” during a fallow “window” within a production cropping system.Field Day participants will get a close look at a replicated warm season cover crop trial at the PMC with 11 species and four cowpea cultivars after 60 days of growth.
Date: August 22, 2018
Time: 11:00 AM - 12:00 PM
Location: Lockeford Plant Materials Center
Tentative Agenda
10:00 - Margaret Smither-Kopperl, PMC Manager - Welcome
10:05 - Scott Park - A Producers Experience with Warm Season Cover Crops
10:25 - Valerie Bullard, PMC Agronomist - Warm Season Cover Crops
10:50 - Gill Costa, Sentek Technologies - Moisture Sensors for Irrigation Water Monitoring
11:10 - Michelle Leinefelder-Miles and Brenna Aegerter, UC Extension - Cover crops, Soil Health and Greenhouse Gas Study
11:30 - Z. Kabir, NRCS Regional Soil Health Specialist - Timing of Warm Season Cover Crops
11:45 - Wendy Rash, District Conservationist - NRCS Programs and Cover Crops
11:55 - Margaret Smither-Kopperl - Conclusions and Questions
3. Annual California Rice Field Day
The purpose of the Rice Field Day is to give rice growers and opportunity to observe and discuss research in progress at the RES. Program highlights will include information about variety improvement, disease resistance, and insect and weed control.
Date: August 29, 2018
Time: 7:30 AM - 1:30 PM
Location: California Rice Experiment Station
Agenda:
7:30-8:30 a.m. Registration, posters and demonstrations
8:30-9:15 a.m. General session: CCRRF membership report, rice research trust report, California rice industry award
9:30-12:00 p.m. Field tours of rice research: variety improvement, disease resistance, insect control, weed control
12:00 p.m. Lunch
/span>
- Author: Michelle Leinfelder-Miles
I sent plant samples to the UC Davis Plant Pathology Diagnostics lab for confirmation on disease. Rather than Rhizoctonia, the lab identified Fusarium oxysporum on all of the plant tissue submitted. While Fusarium oxysporum is the causal agent of Fusarium wilt (a.k.a. Fusarium yellows), the symptoms on these plants indicated root and crown rot, and NOT yellows. Fusarium root rot is common on other beans; however, it has not been a common problem in California limas. For this particular field, its cropping history has been various vegetables for the last couple years, including tomatoes with a severe Fusarium problem in 2016. Rotating out of beans or vegetables to grains would be a good management strategy for future years because Fusarium can live in the soil for several years. Fungicide seed treatments may also help. In this particular case, we talked about managing water well to try to avoid moisture stress (too much or too little) of the current crop to optimize the crop that is there. The grower and PCA assured me that they can manage the moisture well with the drip irrigation on this soil type. For future bean planting, waiting until soil temperature is warmer and not planting as deep would also be important strategies.
- Author: Michelle Leinfelder-Miles
I sent plant samples to the UC Davis Plant Pathology Diagnostics lab for confirmation on disease. Rather than Rhizoctonia, the lab identified Fusarium oxysporum on all of the plant tissue submitted. While Fusarium oxysporum is the causal agent of Fusarium wilt (a.k.a. Fusarium yellows), the symptoms on these plants indicated root and crown rot, and NOT yellows. Fusarium root rot is common on other beans; however, it has not been a common problem in California limas. For this particular field, its cropping history has been various vegetables for the last couple years, including tomatoes with a severe Fusarium problem in 2016. Rotating out of beans or vegetables to grains would be a good management strategy for future years because Fusarium can live in the soil for several years. Fungicide seed treatments may also help. In this particular case, we talked about managing water well to try to avoid moisture stress (too much or too little) of the current crop to optimize the crop that is there. The grower and PCA assured me that they can manage the moisture well with the drip irrigation on this soil type. For future bean planting, waiting until soil temperature is warmer and not planting as deep would also be important strategies.