- Author: Reggie Ellis @Reggie_SGN
VISALIA – Last week's California Citrus Conference marked a major milestone for growers, and it wasn't just the 50th anniversary of the Visalia-based Citrus Research Board (CRB). It was a resounding revelation that new research may cure the greatest threat to the citrus industry in the next few years.
Michelle Heck, PhD, told the crowd of citrus growers at the Wyndham Hotel on Oct. 10 that her team might only need that much time to inbreed a generation of Asian citrus psyllids that are incapable of transmitting the deadly tree disease known as huanglongbing (HLB). The disease has already destroyed China's citrus industry, decimated Florida and Texas growing regions and is currently killing the citrus industry in Brazil.
One grower commented, “China's been dealing with this for 100 years and Brazil for 14 years. We've had this for four to five years in California and we are already knocking on the door of nailing it. That's impressive!”
Heck, a molecular biologist with the USDA Agricultural Research Service, was the first to lead a team of scientists to study the proteins involved in the interaction of the pest, plant and pathogen. One of those proteins creates a blue color in the blood of some psyllids. Her research revealed that psyllids containing the blue protein are far less efficient at transmitting HLB to the plant than others. She then bred those psyllids and took their progency and raised them on orange jasmine hedges, better known as Murraya, a plant the psyllids are attracted but is HLB resistant. The combination of the pest and plant reduced transmission of HLB to healthy citrus leaves from 32% to 2.9%.
Heck said the next steps are to continue breeding the pests that are poor transmitters of the disease to create a line of psyllids that do not transmit HLB at all. She said it would take another two years to breed an “optimized line” of the psyllid but once that was complete, that line could begin mass breeding for release.
“By sheer numbers, we can tip the scales [in the fight against HLB],” she said, “but it's unknown if these lines will out compete other psyllids [in the field].”
One grower asked if the non-transmitting line of the pest would be considered a genetically modified organism, or GMO, a distinction that could hurt fruit grown in groves with the new pest. Heck said all of the psyllids would be bred natuarally, so there is no genetic alteration of the insect itself.
“This is something the anti-GMO groups should feel good about,” Heck said.
Best Case Scenario
Victoria Hornbaker, Statewide Citrus Program Manager for the California Department of Food and Agriculture (CDFA), called the current HLB situation in California a best case scenario. She said the Citrus Pest and Disease Prevention Program's (CPDPP) No. 1 priority is to quickly detect and remove diseased trees. Shortly after the discovery of the first HLB tree in 2012, California's myriad of citrus agencies worked together to quickly implement measures to control movement of fruit and nursery stock, monitor and suppress the ACP population, and begin working on ways to detect the disease and possibly cure it.
“Instead of all commercial groves being covered by a quarantine, we said we're going to quarantine the whole state,” Hornbaker said.
By limiting the movement of citrus in and out of different quarantine zones, there is less likelihood of transporting trees from an infected area to an uninfected area. If any infected trees are discovered, they are removed, destroyed and replaced with a healthy tree. There are many early detection techniques (EDTs) being studied throughout the country, including looking for patterns in leaves, chemicals produced by trees in response to HLB, and studying molecules of the bacteria causing the disease. A recent analysis of these EDTs showed that most are about 95% effective in identifying an infected tree, and that losing 5% of healthy trees is an acceptable loss compared to devastation caused by the disease spreading unchecked.
While early detection methods of ACP are still being perfected, the fight to control the spread of the psyllid is not. After research identified the microscopic parasitic wasp radiate terminaxia as the natural enemy of the psyllid, they began working to mass produce and release them. To date, more than 11 million wasps have bee released in citrus growing regions since 2013, the closest being in Kern County.
Reproduced from Sun Gazette:
- Author: Ben Faber
This is a friendly reminder that the Fall ACP Area Wide Management treatment windows for Santa Barbara County are currently under way -- schedule provided below. Please be sure to notify beekeepers in your area before treating, and file your use reports with the county ASAP after finishing to ensure your treatment is acknowledged.
Thank you to those who have already treated and filed, and those with pending treatments scheduled. The rain forecasted for this week may delay treatments, please just treat when you are able to get back into your orchard. Thank you.
2018 Fall Treatment Schedule
Carpinteria, Summerland, Montecito : Sept 16 to Sept 29
Santa Barbara, Goleta, Gaviota, Santa Maria etc : Sept 23 - Oct 6
CITRUS REMOVAL PROGRAM: If you have, or know of, unloved citrus that is not being cared for, the Citrus Matters ACT NOW program through CCM may be able to assist in removing it. Call 1-844-STOP-HLB (1-844-786-7452) for more information, or contact Joel Reyes at firstname.lastname@example.org or (559) 592-3790. Abandoned or neglected citrus can also be reported to the County Ag Department.
Huanglongbing (HLB) Update
The most recent map and totals for HLB detections are posted at the website citrusinsider.org/maps/ . As of September 28 the total number of trees that have tested positive for the HLB bacterium is 874, all in Los Angeles, Orange and Riverside Counties, plus a single ACP from San Bernardino that tested positive. The most recent expansion to the HLB quarantine area is in Tustin, in Orange County. All HLB detections have been on residential properties and the infected trees have been or are being removed. No HLB has been found in commercial groves to date.
UPCOMING MEETINGS -- Agendas Attached
- The CPDPC Operations Subcommittee meets Wed., October 3 at 9 am in Visalia. Field cleaning protocols are on the agenda again.
- The CPDPC Outreach Subcommittee meets Wed., October 3 at 1:30 pm in Visalia.
- Regulatory Task Force meets October 12 at 1 pm via webinar. Mitigations for moving bulk fruit across quarantine zones will be reviewed, including field cleaning.
- All meetings are open to the public and free to attend. Agendas for all program meetings, including webinar information, can be found here, along with minutes from previous meetings: www.cdfa.ca.gov/citruscommittee/
Useful Links for Area Wide Management
Summaries of the latest scientific research on combating HLB: http://ucanr.edu/sites/scienceforcitrushealth/
UC recommendations for checking your trees for ACP:
UC-recommended ACP insecticides and treatment protocols, including broad, soft and organic options:
For general updates and information on the state ACP/HLB program and regional activities, go to http://citrusinsider.org/
ACP Regional Quarantine Information for Santa Barbara County:
To move bulk citrus outside of your quarantine zone (Santa Barbara/Ventura County) you must have a compliance agreement from CDFA and follow the instructions therein. A copy of the compliance information for growers is here: http://phpps.cdfa.ca.gov/PE/InteriorExclusion/pdf/acpgrowerinformation.pdf
Contact the County Ag Department/Ag Commissioner's Office (805 681-5600) for more information on the regional quarantine for bulk fruit movement.
Please keep in mind that the quarantine compliance program for moving bulk fruit is a separate and distinct program and protocol from the Area Wide Management program detailed in this email. Please feel free to contact me with any questions regarding the ACP Area Wide Management program.
ACP/HLB Grower Liaison
Ventura, Santa Barbara and San Luis Obispo Counties
2018 California Citrus Conference
CLICK HERE TO REGISTER
CLICK HERE TO VIEW EVENT FLYER/h1>/h1>/h1>
- Author: Sonia Rios
The University of California Cooperative Extension is hosting free workshops for citrus grove owners, managers and farmers. The workshop will provide an overview of proper Asian citrus psyllid (ACP) scouting techniques from University of California research entomologists Dr. Monique Rivera. Attendees will have the opportunity to practice psyllid scouting techniques in blocks of trees known to host ACP.
- No cost to attend this event
- Strongly encouraged to bring a hand lens (a loaner hand lens will be provided if needed).
- 1.5 of “other” DPR Continuing Education Hours will be given.
- Further details on workshop location will be provided to registrants by email 48 hours prior to the event.
Space is limited, please register at: http://ucanr.edu/survey/survey.cfm?surveynumber=25658
October 2, 2018, 9-11 AM
If you have any questions, please contact:
951-683-6491 EXT 224
- Author: Ben Faber
- Author: Sara Garcia Figuera, Jennifer Reed and Brianna McGuire
Western Plant Protection Network at UC Davis
Early detection technologies (EDTs) are tests that indicate the presence of disease before signs or symptoms of the disease can be seen. In the same way that a doc-tor measures a patient's blood pressure to look for heart problems, a grower might use a trained “sniffer” dog to detect changes in a tree that looks healthy but has huanglongbing (HLB) disease. By using the EDT, the grower is able to uncover HLB earlier, and can decide on an early, cost-saving course of action.
In the case of HLB, there are many EDTs under development. Some of them look for patterns in the microorganisms that live on the citrus leaves (Leveau snapshot); some look for patterns in the chemicals that are produced by the tree in response to HLB (Pourreza, Davis and Slupsky); and others look for the molecules that the bacterium injects in the tree to cause disease (Ma). A description of some of these EDTs can be found on the Science for Citrus Health website.
Why do we need EDTs for HLB?
To understand why EDTs are needed and what their potential value is, it is necessary to understand the difference between the incubation period for a disease and the latent period. The incubation period is the time between exposure to the pathogen and the appearance of symptoms. The latent period is the time between exposure and the newly-infected host becoming infectious. Huanglongbing (HLB) has a long incubation period and a very short latent period, which means that a tree can be dis-eased for a long time without showing any visible symptoms, while being infectious for a large fraction of that time. Even if a tree does not seem diseased, it can serve as a home for the bacterium (Candidatus Liberibacter asiaticus, CLas) that causes HLB. If a psyllid feeds on the infected tissue of a tree (with or without symptoms), CLas that is present in the leaf tissue can be picked up by the insect and transmitted to other trees when the psyllid moves on to feed. Information from an EDT can help a grower detect the disease in a tree a long time before it would be detected by eye. This cuts down the time psyllids are able to feed on it and transmit the disease, slowing the spread of HLB to neighboring trees.
Why is it important to remove infected trees as early as possible?
If a tree that tests positive for CLas is not treated or removed, the bacterium will spread throughout the tree. Over time, an increasing proportion of the tree's tissues will become infected, increasing the chances that a psyllid will become infected upon feeding, and subsequently spread the infection to healthy neighboring trees. If the infected tree is removed, there is no opportunity for psyllids to feed on the infected tissue and spread the disease. Once CLas is detected, tree removal is the only surefire way to prevent the spread of the infection, and it is extremely time-sensitive. The sooner an infected tree is removed, the lower the chances that psyllids will get infected. The savings associated with early infected tree removal will be proportional to the amount of surrounding trees that would have been infected with CLas due to that tree, and the number of months that it would be left on the ground.
Who is working on the project?
Several research teams in different universities and research stations, supported by a variety of funding organizations, have been working on the development of a variety of EDTs. These EDTs, designed under laboratory and greenhouse conditions, are being validated under field conditions in Texas and Florida. In California, where HLB has not been detected in citrus orchards, samples of different citrus varieties have been collected from healthy trees and trees affected by other diseases from all over the state. These samples are being used to calibrate the EDTs, and to test if they can distinguish between healthy and HLB-diseased trees, and between HLB-diseased trees and trees affected by other common citrus diseases. Dr. Neil McRoberts and his team at UC Davis are evaluating the data from these experiments and providing support to the EDT researchers.
What are the challenges and opportunities?
Currently, regulations require HLB infected trees to be removed if a certain amount of CLas DNA is detected in leaf samples through polymerase chain reaction (PCR). However, CLas is unevenly distributed in the sap of citrus trees, and the leaf samples collected might not be PCR-positive even though the bacterium is already present elsewhere in the tree. EDTs offer the possibility to detect infected trees before they are PCR-positive, so they could be removed earlier in the HLB epidemic. Therefore, the value of EDTs relies on the voluntary removal of EDT-positive trees before the law requires them to be removed.
No EDT gives perfect diagnostic results. Sometimes healthy trees will produce EDT scores that look like diseased trees (so-called “false positives”). Removing such trees will result in an immediate financial loss. However, because the economic damage caused by leaving an infected tree in place is much bigger than the value of a healthy tree, using an EDT to guide decisions has the potential to result in a long-term economic benefit to individual growers and communities, by reducing the spread of HLB. Losing a few healthy trees along the way is the unavoidable cost of stopping the disease from spreading. Like-wise, some trees will seem healthy based on EDT scores but might end up showing symptoms (“false negatives”). The proportion of true positives, false positives, true negatives and false negatives represents the accuracy of a diagnostic test. Dr. McRoberts' team is analyzing the accuracy of the EDTs, and preliminary results suggest that the best performing EDTs could be correctly determining the status of the trees 95% of the time.
The results of this analysis could be used to foster the adoption of EDTs among the citrus grower community, promoting the idea that the sooner infected trees are detected and removed, the smaller impact HLB will have on California's citrus production. Unless there is sufficient cooperation in integrated management of HLB by removing infected trees as early as possible, controlling the ACP on an area-wide scale, and using certified plant material, the California citrus industry is likely to suffer un-sustainable economic losses to HLB.