- Author: Ben Faber
IMMOKALEE, Fla. — University of Florida scientists are working toward establishing a new biological method that may help farmers control the insect that transmits the deadly greening disease into citrus trees. Greening is present in about 95 percent of the citrus trees in Florida, so by using a virus that may kill the insect, growers may be able to reduce the need for pesticides.
Instead of spraying insecticides, scientists hope to harness the natural enemies of the tiny Asian citrus psyllid to manage the invasive pest, said Ozgur Batuman, a plant pathologist at the UF/IFAS Southwest Florida Research and Education Center in Immokalee.
Batuman is leading a UF/IFAS research team investigating viruses that live in the digestive system of the psyllid. They want to see whether any of them can weaken or kill the insect.
The psyllid transmits the bacterium responsible for greening by feeding on a citrus tree's new shoots and leaves.
UF/IFAS scientists are getting promising early results with this research. Their latest research suggests a natural process that would kill the insect or at least prevent greening from being transmitted to citrus trees.
“This invasive pest is now established throughout Florida's commercial groves, so growers use insecticide sprays that are potentially harmful for the environment as one of their primary tactics for fighting citrus greening,” Batuman said. “By reducing psyllid populations in their groves, growers hope to increase the quality of fruits and the productive lives of their trees by minimizing the number of times a tree is exposed to the greening pathogen.”
To arrive at their results, Batuman and his team spent two years collecting psyllids from commercial citrus groves in 22 central and south Florida counties – from Lake and Orange counties in the north to Martin County in the southeast to Collier County in the southwest.
They identified viruses within the psyllids' bodies.
By using a test that amplifies DNA, scientists found five viruses in the guts of the psyllids they collected. They believe they can use those viruses to control the psyllids that live in the very groves from which scientists collected them.
With these experiments, for the first time, scientists have taken big strides toward identifying viruses associated with the Florida psyllids. They also now better understand the presence of those viruses in the psyllids. Asian citrus psyllids first arrived in southeast Florida in 1998.
“Future experiments will investigate how these viruses can be manipulated so that they may alter the pysllid's biology,” said Batuman. “We also need to find out how the viruses affect survival and transmission of the bacterium that causes citrus greening disease, also known as Huanglongbing, or HLB.”
“By understanding how the viruses interact with the psyllid biology, we may be able to understand how to better control the psyllids,” he said.
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By: Brad Buck, 813-757-2224, bradbuck@ufl.edu, 352-875-2641 (cell)
- Author: Ben Faber
Citrus greening disease, or Huanglongbing (HLB), is deadly, incurable, and the most significant threat to the citrus industry. Most HLB research focuses on the tree canopy, but scientists in California studied the impact of HLB on root systems. They recently published the first study to report on the response of two different varieties of citrus to the causal bacterium, 'Candidatus Liberibacter asiaticus' using metabolomics and microbiome technologies.
"Metabolomics is a cutting-edge field of study that provides snapshot information about the metabolism of living things," explains author Emily M. T. Padhi, "while microbiome studies provide valuable information about the microbial communities living in a particular ecological niche - some microbes are beneficial to the host, while others can be harmful."
Padhi and colleagues wanted to see how the root system of two varieties of citrus responded to HLB. They collected roots from healthy and infected Lisbon lemon and Washington Navel orange trees grown in greenhouses at the same time and under the same conditions.
They found that both varieties experienced a reduction in root sugars and amino acids when exposed to HLB. However, they also found differences. While the concentration of malic acid and quinic acid (two metabolites involved in plant defense) increased in the navel roots, they decreased in the lemon roots. They also found that the beneficial bacteria Burkholderia increased substantially in navel plants but not in lemons, which contradicts previous studies.
"Overall, this is the first study to compare two varieties of citrus using a combined metabolomics and microbiome approach and demonstrates that scion influences root microbial community composition and, to a lesser extent, the root metabolome."
There is evidence to suggest that the causal bacterium moves to the root system soon after a plant becomes infected. A key strategy for preserving the health of an infected tree is root system management and research on different responses to HLB may help devise new variety-specific preventative and treatment measures.
MAGE: Images of the bulk root mass and sample leaves from healthy and 'Candidatus Liberibacter asiaticus' lemon and navel plants.
Credit: Emily M. T. Padhi, Nilesh Maharaj, Shin-Yi Lin, Darya O. Mishchuk, Elizabeth Chin, Kris Godfrey, Elizabeth Foster, Marylou Polek, Johan H. J. Leveau, and Carolyn M. Slupsky
- Author: Ben Faber
Citrus greening disease, or Huanglongbing (HLB), is deadly, incurable, and the most significant threat to the citrus industry. Most HLB research focuses on the tree canopy, but scientists in California studied the impact of HLB on root systems. They recently published the first study to report on the response of two different varieties of citrus to the causal bacterium, 'Candidatus Liberibacter asiaticus' using metabolomics and microbiome technologies.
"Metabolomics is a cutting-edge field of study that provides snapshot information about the metabolism of living things," explains author Emily M. T. Padhi, "while microbiome studies provide valuable information about the microbial communities living in a particular ecological niche - some microbes are beneficial to the host, while others can be harmful."
Padhi and colleagues wanted to see how the root system of two varieties of citrus responded to HLB. They collected roots from healthy and infected Lisbon lemon and Washington Navel orange trees grown in greenhouses at the same time and under the same conditions.
They found that both varieties experienced a reduction in root sugars and amino acids when exposed to HLB. However, they also found differences. While the concentration of malic acid and quinic acid (two metabolites involved in plant defense) increased in the navel roots, they decreased in the lemon roots. They also found that the beneficial bacteria Burkholderia increased substantially in navel plants but not in lemons, which contradicts previous studies.
"Overall, this is the first study to compare two varieties of citrus using a combined metabolomics and microbiome approach and demonstrates that scion influences root microbial community composition and, to a lesser extent, the root metabolome."
There is evidence to suggest that the causal bacterium moves to the root system soon after a plant becomes infected. A key strategy for preserving the health of an infected tree is root system management and research on different responses to HLB may help devise new variety-specific preventative and treatment measures.
Emily M. T. Padhi Nilesh Maharaj Shin-Yi Lin Darya O. Mishchuk Elizabeth Chin Kris Godfrey Elizabeth Foster Marylou Polek Johan H. J. Leveau and Carolyn M. Slupsky
https://apsjournals.apsnet.org/doi/10.1094/PHYTO-03-19-0103-R
Images of the bulk root mass and sample leaves from healthy and 'Candidatus Liberibacter asiaticus' lemon and navel plants.
Credit: Emily M. T. Padhi, Nilesh Maharaj, Shin-Yi Lin, Darya O. Mishchuk, Elizabeth Chin, Kris Godfrey, Elizabeth Foster, Marylou Polek, Johan H. J. Leveau, and Carolyn M. Slupsky
/h4>- Author: Ben Faber
The following is compiled from the January newsletter of the Ventura County ACP-HLB Task Force
Results of November scouting trip are available for the Canine Detection Team
A team of six dogs and three handlers from F1K9 scouted 20 citrus ranches in Ventura County between Nov. 18 and Nov. 22, 2019. The visit included returns to several ranches scouted during F1K9's July deployment, as well as numerous ranches in new areas. A total of 4,650 trees were inspected, and dogs alerted on 353 (8%). Alerts occurred at every location. The percentage of scouted trees that triggered alerts at each ranch or block ranged from 3% to 22%. Download the full report here.
The canine detection team is returning next week to scout more orchards. However, their time is fully allocated. Planning is under way for their more permanent return by February or March 2020. If you wish to have your grove(s) scouted in the future, please send an email indicating your interest to Farm Bureau CEO John Krist at john@farmbureauvc.com.
HLB update
A total of 1,760 residential citrus trees have been confirmed PCR-positive for HLB in San Bernardino, Riverside, Los Angeles, and Orange counties. Information about the expanded HLB quarantine, and a tally of the HLB confirmations (updated weekly) can be found at CitrusInsider.org. Regulatory actions required by the state in response to an HLB detection are detailed in CDFA's Action Plan (https://www.cdfa.ca.gov/citruscommittee/docs/ActionPlan.pdf). To see the proximity of your citrus to the nearest confirmed HLB, you can enter an address in this Google maps-style website: www.ucanr.edu/hlbgrowerapp. The site also provides a direct link to the HLB Voluntary Best Practices most relevant to your location.
AWM update
The winter ACP area-wide management treatments have begun, and treatment reminders have been distributed. If you did not receive a reminder, please contact grower liaison Sandra Zwaal (szwaal2@gmail.com) or Cressida Silvers (cressidasb@gmail.com) to be added to the distribution list.
Twenty-four of Ventura County's 50 psyllid management areas (PMAs) qualified for the winter buffer treatments, in which the California Department of Food and Agriculture will apply pesticides to residential citrus within 400 meters of commercial groves. The requirements to qualify for residential buffer treatments are expected to change slightly in the future. Stay tuned for the UC recommendations and a vote from the Citrus Pest and Disease Prevention Committee (CPDPC) on the new requirements.
Report neglected and abandoned citrus
Help prevent neglected and abandoned citrus from serving as a breeding ground for ACP and the spread of HLB by reporting its location to the County Agricultural Commissioner's office at (805) 388-4222. If your citrus is not worth the resources required to protect it from ACP and HLB, it may be a good time to consider removing the trees.
Calendar
The next CPDPC meeting will be on Jan. 15. Click here to download the agenda.The CPDPC makes decisions on behalf of the citrus industry, and attendance by all citrus growers and affiliates is encouraged. The Coastal Region committee representative is Kevin Ball; contact him at kevin.ball@aglandca.com. Meetings are free and open to the public, and can be attended in person, via webinar, or by phone. The agenda and prior meeting minutes can also be found at https://www.cdfa.ca.gov/citruscommittee/.
The 9th Annual UC Riverside Citrus Field Day for citrus growers and citrus industry representatives is Jan. 29. Click here to download the agenda and registration information.
The University of California has developed a series of one-hour webinars, designed for growers and pest control advisors, that will highlight various pest management and horticultural topics for citrus and avocados. During each session, a UC expert on the subject will make a presentation and entertain write-in questions via chat during and/or after the presentation. To learn more, go to https://ucanr.edu/sites/ucexpertstalk/.
Resources
University of California ACP area-wide materials list and ACP monitoring protocols
Movement of bulk citrus materials list
Ventura County AWM maps and schedule
Citrus Pest and Disease Prevention Program
Ventura County ACP-HLB Task Force mailing list signup
Contact your grower liaisons if you have additional questions:
Sandra Zwaal
(949) 636-7089
Cressida Silvers
(805) 284-3310
- Author: Ben Faber
ACP Management for Commercial Growers - UC Ag Expert Webinar, Dec 4 @3 p.m.
Take advantage of this opportunity for an interactive web-based presentation on ACP field management from UC researcher and ACP expert Dr. Beth Grafton-Cardwell. You don't have to travel for this one, it's free, and you can earn CEUs, too! Sign up here: https://ucanr.zoom.us/webinar/register/WN_fEKM2ScPTk6WF5ilga6V7Q
HLB Update
In San Bernardino County a single residential tree tested positive for the bacterium that causes HLB. As a result, the HLB quarantine has been expanded in the Montclair area. Also of note is an adult ACP that recently tested positive for the bacterium that causes HLB near Corona, outside of the HLB quarantine. See the latest HLB map for details: maps.cdfa.ca.gov/WeeklyACPMaps/HLBWeb/HLB_Treatments.pdf. As before, all HLB detections to date have been on residential properties, the infected trees have been or are being removed, and ACP treatments are applied on a recurring basis to remaining citrus in those areas. No HLB has been found in commercial groves via PCR testing.
Regulatory responses required by the state in response to an HLB detection are described in CDFA's Action Plan for ACP and HLB.
How Close Is HLB To Your Citrus? There's a New UC App For That!
Visit ucanr.edu/hlbgrowerapp , zoom to or type in your location and it shows your proximity to HLB+ detections, recommends best practices to protect your citrus from HLB based on your current proximity to know detections, and provides a link to the Voluntary Grower Response Plan for more information. As HLB detections via PCR 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.
CITRUS REMOVAL PROGRAM: Citrus trees that are neglected or abandoned may harbor ACP and HLB, increasing risk to other citrus in the area. Abandoned and neglected trees may be reported to me or the county Ag Commissioner's office. The Citrus Matters ACT NOW program may be able to assist in citrus removal. For more information contact Joel Reyes at jreyes@cacitrusmutual.com or (559) 592-3790.
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
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Cressida Silvers
CA Citrus Pest and Disease Prevention Program
ACP/HLB Grower Liaison
Ventura, Santa Barbara and San Luis Obispo Counties
805 284-3310 (phone or text)