- Author: Jeanette Warnert
The city of Riverside pitched a white tent over the "Parent Navel" orange tree at the intersection of Arlington and Magnolia avenues last week to protect it from the threat of huanglongbing disease, reported Ryan Hagen the Riverside Press Enterprise.
“The Parent Navel is an iconic symbol of Riverside, as it represents the impact the citrus industry had on our economy,” Mayor Rusty Bailey said in a press release issued by the City of Riverside. “Riversiders hold this symbol of our citrus heritage very dear, so it is encouraging to see our parks personnel taking a proactive approach.”
The tree was one of two planted by Eliza Tibbets in 1873, when she received the seedless orange cultivars from Florida by mail. Tibbets cared for the trees and sold budwood to nurseries, which led to extensive plantings of nursery trees cloned from hers.
Huanglongbing disease made its appearance in Riverside last year in residential trees. Officials are working to prevent its spread by controlling Asian citrus psyllid, the insect that can move the disease from tree to tree. Meanwhile researchers are searching for a cure.
The Parent Navel's high value led UC Riverside researchers and city officials to construct the large white barrier.
"It's not beautiful," said Georgios Vidalakis, UC Cooperative Extension specialist and director of the citrus clonal protection program at UC Riverside. "It's obstructing the tree from public view, and we apologize for that. But the risk from not doing that is catastrophic."
The Citrus Research and Development Foundation (CRDF), a $124 million state citrus-industry initiative, has invested nearly 90 percent of its funds in HLB research. CRDF asked the Academies to review its research portfolio and determine if its efforts have followed recommendations outlined in the Academies' 2010 report, which originally called for the organization's creation. The committee found that CRDF was responsive to several recommendations from the previous report, and along with other funders, has advanced our knowledge about the disease. However, HLB remains a serious danger to Florida's citrus industry, having progressed from an acute to a chronic disease throughout the state.
The report notes that significant barriers to progress toward an HLB solution still exist, among them the inability to culture the bacteria in the laboratory, the lack of advanced diagnostics for early disease detection, and the absence of standardized research methodology that would improve the comparability of results across studies. Resolution of any one of these issues would constitute a significant step, according to the report.
The committee recommended continuing support for both basic and applied research for short- and long-term research efforts. In the long run, HLB solutions would likely utilize new technology, such as gene modification and gene editing, focusing on targets that mediate molecular interactions among plant, bacteria, and the vector, the committee said. As interest in using genetic modification in research grows, CRDF should also consider funding research to assess stakeholder acceptance of the technology and expand efforts to educate growers, processors, and consumers to facilitate the eventual deployment of genetically modified citrus lines.
In the meantime, growers in the state will need short-term solutions for the industry to remain viable. The report recommends finding the best suite of strategies to control the disease in different environmental and growing conditions, vector and pathogen pressures, tree varieties, and stages of tree health, which would help growers in Florida and other states where HLB also occurs.
The report also highlights the need to better understand the economic and sociological factors that impact decision-making and behaviors of growers, which influence the adoption of HLB management strategies. CRDF should create accessible databases to support sociological and economic modeling of citrus greening-related research outcomes and application projections.
The report recommends researchers communicate about the outcomes and evaluation of their efforts in a timely and systematic way. Additionally, current approaches to research prioritization and funding based within individual federal and state funding agencies have not led to development of a master plan for HLB research and subsequent management solutions. CRDF should work with other funding agencies to create an overarching advisory panel to develop a master plan for HLB research, communication, and management.
The study was sponsored by CRDF. The National Academies of Sciences, Engineering, and Medicine are private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, technology, and medicine. The National Academies operate under an 1863 congressional charter to the National Academy of Sciences, signed by President Lincoln. For more information, visit http://national-academies.org. A roster follows.
To download full report: https://www.nap.edu/read/25026/chapter/1
Citrus Grower Workshop REMINDER (April 26)
Dr. Beth Grafton-Cardwell will present findings from her continuing survey of ACP populations across Ventura County, including data on the effects of pesticide treatments on ACP abundance. Other speakers will present updates on the statewide Citrus Pest and Disease Prevention Program, the status of Huanglongbing disease in California, grower participation in the local ACP suppression effort, and updates to the Fall 2018 ACP area-wide treatment schedule. The workshop will be from 9:30 to 11:30 a.m. on Thursday, April 26, at the Agriculture Museum, 929 Railroad Ave., Santa Paula. Attendance is free, but advance registration is required. Please register online at: https://vctaskforce-workshop.eventbrite.com.
The number of trees confirmed as being infected by HLB has reached 552 (321 in Orange County, 228 in Los Angeles County and 3 in Riverside County). All were in residential settings, not commercial groves. The HLB quarantine boundaries and the latest tally of HLB confirmations, updated weekly, is available online at https://citrusinsider.org/maps/. As confirmations increase and spread closer to commercial citrus, it is a good time to consider removing citrus trees not worth the resources required to protect them from ACP and HLB.
ACP Areawide Treatments
Thank you to those submitting timely ACP treatment pesticide use reports (PURs) and providing the grower liaisons with updates such as contact information and farm manager/applicator/PCA changes. This helps ensure ACP treatments are immediately recognized, and allows more effective communication with growers.
The Spring uncoordinated ACP treatment window begins now through July 15. Although these treatments are not coordinated, psyllid populations must be kept low to reduce the risk of HLB. Scout/monitor and treat if you see ACP, and use an ACP-effective material during spring/summer management. Click here for University of California recommendations for ACP monitoring.
The Citrus Pest and Disease Prevention Committee will meet May 9 in Ventura. Attendance is free. Here is a link to the CDFA site with agenda, venue, and webinar information: https://www.cdfa.ca.gov/citruscommittee/.
Feel free to contact your grower liaisons if you have questions, or need pest-control or tree-removal referrals.
For the past 18 months, a team led by University of California research entomologist Beth Grafton-Cardwell has been conducting an Asian citrus psyllid monitoring project to determine the efficacy of Ventura County's area-wide ACP suppression strategy. Based on her analysis of the survey data, Dr. Grafton-Cardwell has recommended changes in the area-wide management (AWM) protocol to provide better control of the invasive pest. The Ventura County ACP-HLB Task Force has endorsed her recommendations and incorporated them into the AWM schedule for 2018-2019.
The primary change will be the addition of a second fall treatment, which may be a perimeter spray, for lemons and mandarins. Fall is when ACP populations reach their highest level, and the research data indicate a single pesticide application is inadequate. The research data also show that ACP is most abundant on grove perimeters, and only expands into the center rows when the population is large. In recognition of this, the new Task Force protocol allows one of the two fall applications to be applied to only the grove perimeter, as long as the grower, grove manager or PCA/PCO has scouted the orchard and determined that center rows are free of ACP nymphs on flush. The other fall application, however, must cover the entire grove.
As in previous cycles, the treatment window for each psyllid management area (PMA) will last three weeks, but it now will overlap with the next window by two weeks instead of one. This will compress each treatment cycle from four months in length to two and a half months, heightening the area-wide effect. (See below for the schedule.)
The annual AWM program for lemons and mandarins will now consist of four applications: a coordinated AWM whole-orchard treatment in winter, individual applications of an ACP-effective material (either alone or piggybacked on a spray for another pest) in late spring-early summer, and two coordinated AWM treatments in late summer and fall (one of which may be a perimeter spray).
The annual cycle for oranges, which do not flush year-round, remains two coordinated applications, one during the first fall window and one in the winter. For organic growers, each "treatment" must consist of two applications of Entrust and oil or Pyganic and oil, or other approved alternative material, to compensate for their limited residual activity. The list of approved materials for both conventional and organic operations is at http://ipm.ucanr.edu/PMG/r107304411.html.
Members of the Ventura County citrus community are invited to a workshop to learn more about these changes, and the research data upon which they are based. The workshop will be from 9:30 to 11:30 a.m. on Thursday, April 26, at the Agriculture Museum, 929 Railroad Ave., Santa Paula. Attendance is free, but advance registration is required. Please register online at: https://vctaskforce-workshop.eventbrite.com.
During the workshop, Dr. Grafton-Cardwell will present findings from her continuing survey of ACP populations across the county, including data on the effects of AWM pesticide treatments on ACP abundance. Other speakers will present updates on the statewide Citrus Pest and Disease Prevention Program, the status of Huanglongbing disease in California, and grower participation in the local ACP suppression effort.
The Task Force is also planning outdoor workshops to help grove owners, managers or farm employees develop an effective ACP scouting strategy. Topics will include how to scout for ACP, and how to identify symptoms of HLB. More information will be distributed in coming weeks.
The following is the new schedule for Fall 2018 and Winter 2019 treatments, organized by groups of PMAs. Overview maps of Ventura County's PMA boundaries are available at http://www.farmbureauvc.com/issues/pest-issues/asian-citrus-psyllid#task-force.
Individual maps of Ventura County's PMA boundaries, along with many other documents pertaining to the Ventura County AWM program, can be viewed or downloaded at
As was the case with the previous AWM treatment cycles, growers will be notified about the date of their treatment window either by their packinghouse field reps, their PCAs or by the Ventura County grower liaisons: Sandra Zwaal (firstname.lastname@example.org) and Cressida Silvers (email@example.com). It will be up to growers to work with their PCAs and applicators to schedule those treatments.