A single breakthrough discovery for managing citrus greening in Florida in the future is unlikely, says a new report by the National Academies of Sciences, Engineering, and Medicine.  The committee that wrote the report called for a systems approach to prioritize research on the disease and strategically distribute resources for research to effectively manage the disease, which is the most serious threat for citrus growers worldwide.

The disease Huanglongbing (HLB) or citrus greening — associated with bacteria that are spread by a sucking insect, the Asian citrus psyllid — was initially observed more than 100 years ago in Asia and was first detected in Florida in 2005.  The infection results in blotchy mottling of leaves, stunting of shoots, gradual death of branches, and small, deformed fruits with bitter juice.  Although infected trees do not die right away, they can remain in a steady state of decline for several years.  Between 2010 and 2014, acreage of citrus trees in the state declined from roughly 750,000 to 476,000 acres, and production volume has declined by 58 percent since 2005.  In Florida, citrus greening has caused a cumulative loss of $2.9 billion in grower revenues from 2007 to 2014, an average of $374 million a year. 

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. 

http://www8.nationalacademies.org/onpinews/newsitem.aspx?recordid=25026&_ga=2.42906213.1714981823.1523541734-514267579.1523541734

Get the Report:

http://dels.nas.edu/Report/Review-Citrus-Greening/25026?_ga=2.258315978.1714981823.1523541734-514267579.1523541734

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

bit.ly/VC-AWM-docs.

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 (szwaal2@gmail.com) and Cressida Silvers (cressidasb@gmail.com). It will be up to growers to work with their PCAs and applicators to schedule those treatments.

Two questions and comments came up last week about the use of mulch in orchards. The first is that mulch is two edged. It serves to combat erosion and root rot, but it can also burn. Mulch and wood piled up against tree trunks and near trunks can cause damage to those trunks. A Fillmore grower actually goes through the orchard with a blower to move mulch away from trunks when alerted to fire. On the other hand, irrigated orchards have been shown to be effective at suppressing fire encroaching on homes.

So where to read more about fire? About mulch? Check out some of the blogs from the past.

Phire, Phlood, Phreeze and Fytophthora

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=22760

Mulch and green waste applied to avocado orchards and More

Green Waste, Yard Waste, Whatever You Call It- It has Simple Rules for Use

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=13093

A Safer Source of Inexpensive Orchard Mulch

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=12867

Avocado planting holes

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=6458

Cellulase Production by Various Sources of Mulch

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=6809

A Caution on Free "Compost/Mulch"

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=11712

A Safer Source of Inexpensive Orchard Mulch

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=12867

Mulch, Avocados and the Home Garden

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=14906

Mature Compost Does NOT Kill Phytophthora

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=19856

Use of Mulch in Organic Orchards Called into Question

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=21394