- Author: Ben Faber
Citrus Huanglongbing (HLB), also known as greening, is one of the most serious citrus plant diseases in the world. Infected trees produce bitter fruits that are green, misshapen, and unsuitable for sale. Once a tree is infected, there is no cure and it typically dies within a few years. Greening has already devastated the Florida citrus industry and poses a threat to California and Texas as well as Australia and the Mediterranean region.
Currently the most effective ways to prevent the spread of HLB are to stop the causal agent (Candidatus Liberibacter asiaticus) using quarantine measures, control the insect that spreads the disease (Asian citrus psyllid), remove the diseased trees, and plant HLB free trees. To this end, early diagnosis of HLB-diseased trees is crucial. Traditionally, diagnosis relies on observing blotchy mottle symptoms and confirming disease presence using molecular tools. However, these symptoms do not show until months after disease transmission and by then the disease has likely already spread throughout the grove.
Professor Nian Wang and his postdoctoral research associate Dr. Sheo Shanker Pandey, both from Citrus Research and Education Center, Department of Microbiology and Cell Science, at the Institute of Food and Agricultural Sciences of University of Florida, developed a strategy for early diagnosis of HLB before the appearance of blotchy mottle symptoms. They used a low-cost staining method to identify insect feeding sites and tested those identified sites for the causal agent using quantitative real-time PCR (polymerase chain reaction).
Through this method, the pair were able to detect the HLB causal agent up to two days after transmission and long before the appearance of symptoms. This early detection will enable citrus growers to prevent the spread of HLB in their fields. This finding is especially crucial for California, Texas, Australia, and the Mediterranean region as those areas are currently plagued by HLB.
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More details about this study can be found in "Targeted Early Detection of Citrus Huanglongbing Causal Agent 'Candidatus Liberibacter asiaticus' Before Symptom Expression" in Phytopathology Volume 109, Number 6, published June 2019.
https://apsjournals.apsnet.org/doi/full/10.1094/PHYTO-11-18-0432-R
The appearance of HLB symptoms in 5-month-old cultivar Valencia seedlings fed by Asian citrus psyllid for 2 to 20 days. The HLB symptoms were monitored at 30, 60, and 90 days postinoculation (dpi). Representative images of HLB symptom development are shown. Photo: Sheo Shankar Pandey and Nian Wang
- Author: Ben Faber
From
Cressida Silvers
ACP/HLB Grower Liaison
Ventura, Santa Barbara and San Luis Obispo Counties
805 284-3310
Reminder of 2019 Fall ACP Area Wide Management Schedule
September 8 - 21: Carpinteria, Summerland, Montecito
September 15 - 28: Santa Barbara, Goleta, and the rest of the county
Here is the University of California website on ACP monitoring techniques and management recommendations: ucanr.edu/sites/ACP/Grower_Options/Grower_Management/
If you are restricted in your choice of materials, applications of horticultural oil can be effective.
Remember to notify beekeepers in your area before treating by contacting the County Ag Department at 805 681-5600. Get additional information about the new on-line bee registration and notification system BeeWhere at beewherecalifornia.com .
ACP continues to be difficult to find in the field. This is a good thing, and we want to keep it that way, so please keep up the good work by continuing to monitor your trees and participate in the Area Wide Management Program.
Remember, difficulty finding ACP does not mean it is not present in the orchard, or not in surrounding residential citrus. The fact that ACP adults continue to show up in yellow sticky traps throughout the south county is a reminder of this.
Secretary Ross Visits Santa Barbara County
CDFA Secretary Karen Ross visited Santa Barbara County last month to hear first hand how neighboring cannabis operations are impacting existing agriculture. Several citrus growers, PCAs, applicators, and I had the honor of speaking with Secretary Ross, along with representatives from the governor's office, CDFA, and the county agricultural commissioner's office.
HLB Update
The most recent map and totals for all HLB detections in the state are posted at the website maps.cdfa.ca.gov/WeeklyACPMaps/HLBWeb/HLB_Treatments.pdf. As of August 2, a total of 1,534 trees and 256 ACP have tested positive for the HLB bacterium, on a total of 1,110 sites, all still in LA, Orange, and Riverside Counties. To date, all HLB detections have been on residential properties, the infected trees have been or are being removed, and ACP treatments applied on a recurring basis to remaining citrus in those areas. No HLB has been found in commercial groves.
Voluntary Best Practices for HLB protection
As HLB detections increase and spread, it's important to be aware of possible actions you could take to further protect your citrus should an HLB detection occur in your area. These Voluntary Best Practices can be found at the Citrus Insider website HERE.
Regulatory responses required by the state in response to an HLB detection are described in CDFA's Action Plan for ACP and HLB .
UPCOMING CPDPC MEETINGS -- All meeting agendas and eventually the minutes are posted at www.cdfa.ca.gov/citruscommittee/ . All meetings are free and open to the public, and accessible via phone/webinar.
- Operations and Outreach Subcommittees meeting date has changed to Wed, Aug 21. Outreach agenda is here, Operations Agenda is pending.
Additional Useful Links:
Summaries of the latest scientific research on combating HLB: ucanr.edu/sites/scienceforcitrushealth/
Science-based analyses to guide policy decisions, logistics, and operations: www.datoc.us
General updates and information on the state ACP/HLB program and regional activities: citrusinsider.org
- Author: Ben Faber
- Author: Elizabeth Grafton-Cardwell
- Author: Barbara Alonso
The summer issue of Citrograph has just been released, and our outreach project has been featured. Written by Sara García-Figuera, the article discusses our approach for educating citrus stakeholders, researchers, media and the general public about the nationwide technologies being developed to combat the devastating citrus disease – huanglongbing (HLB). Read more about all the tools available to growers and the general public at http://www.citrusresearch.org/uncategorized/citrograph-summer-2019/#more-8369 (pages 28-30)
- Author: Ben Faber
Voluntary Best Practices for Growers' Response to Huanglongbing
To provide California citrus growers with a strong toolbox of science-supported strategies and tactics to protect their orchards from Huanglongbing, the Citrus Pest & Disease Prevention Committee endorsed a set of best practices for growers to voluntarily employ in response to HLB in California.
The recommendations – which are grouped based on a grower's proximity to an HLB detection – represent the most effective tools known to the citrus industry at this time and are meant to supplement the California Department of Food and Agriculture's required regulatory response. They were developed by a task force consisting of growers from various regions across the state and scientists, including Dr. Beth Grafton-Cardwell and Dr. Neil McRoberts.
Growers are encouraged to use as many methods as feasible for their operation in order to limit the spread of the Asian citrus psyllid (ACP) and HLB, as the cost to manage the Asian citrus psyllid is far less than any potential costs or loss to the industry should HLB take hold throughout our state.
The Best Practices at a Glance
The complete best practices document, which includes the scientific rationale for the best practices, can be downloaded here. The following grid is intended to provide a brief, digestible format of the best practices.
- Author: Ben Faber
At a recent workshop sponsored by the Ventura County ACP-HLB Task Force, presentations were made about the effectiveness of ACP suppression in the county, recommendations for voluntary grower responses to confirmed HLB-positive trees, area-wide treatment participation rates and other topics. The speaker presentations have been posted online, and are available for review at:
