Recipient Organization
UNIVERSITY OF FLORIDA
G022 MCCARTY HALL
GAINESVILLE,FL 32611
Performing Department
(N/A)
Non Technical Summary
The project will determine if individual protective covers (IPC) can be combined with injections of oxytetracycline (OTC) to sustain newly planted citrus trees until they become productive in huanglongbing (HLB) endemic regions. At two sites, we will determine the optimal timing to remove IPCs (12, 18, or 24 months) based on tree health and horticultural measurements, including yield in the 3rd year (one site). Other pests and diseases will be monitored (Obj.1). This will be combined with OTC injections (Obj.2) at intervals (0, 6, or 12 months) after IPC removal and once a year thereafter. We will follow whether trees become infected, the quantity of live bacteria in the trees after injection, and the OTC residues. Furthermore, we will show whether the insect vector can acquire and transmit the bacteria from OTC treated trees (Obj.2a). The costs and benefits of our management techniques will be determined for a comprehensive economic analysis to show that profitability is possible with the right strategies (Obj.3). Finally, field days and other extension programming activities are planned to show growers the outcomes of our work so that they can make management decisions (Obj.4). These objectives address the following ECDRE priority needs, particularly (2) regional management of ACP on commercial citrus groves and (4) strategies for maintaining HLB-infected tree productivity. This proposal combines two promising strategies into one wholistic management plan that could be easily adopted by growers facing endemic HLB, no matter their location.
Animal Health Component
70%
Research Effort Categories
Basic
10%
Applied
70%
Developmental
20%
Goals / Objectives
The overarching goal of our proposed research is to develop a consistent methodology to get trees to a canopy size so they can begin to fruit profitably until a more permanent solution is found.Our goal is to establish new citrus trees with canopies and root systems that are healthy enough to reliably produce saleable fruit in an HLB endemic region such that growers are able to establish new, productive groves. We will demonstrate the combined effect of IPCs and OTC including the best intervals of removing IPCs and injecting OTC after the removal, meeting growers' desire for a strategy to keep young trees healthy once an IPC is removed. This would help growers return to profitability and give trees a healthy start, prolonging when they become infected with the bacterium. It is hoped that OTC could delay infection or significantly mediate the effects of CLas on young healthy tree such that the citrus industry can persist in Florida. We will determine if there are any detrimental outcomes to injecting young trees in the first 3 years. We will also understand how OTC affects the CLas titer, the proportion of living bacteria that remain after injection, and how this changes over time. We will also show whether OTC can prevent acquisition and transmission of CLas by ACP. From this project, new science-based HLB management recommendations and documents for growers will be developed. Furthermore, we will have an economic analysis that will help growers determine the costs of the combined treatments to assist their decisions on whether they should adopt the strategy. We expect the results will be used by growers choosing to use an IPC in combination with OTC at the intervals that we found to be optimal when planting new groves or even possibly resets. This will help restore groves to profitability.Objective 1. Determine the optimal removal interval for individual protective covers (IPCs) to establish productive young citrus trees in huanglongbing endemic regions.Objective 2. Determine the optimal timing to inject oxytetracycline (OTC) after IPC removal to establish productive young citrus trees in huanglongbing endemic regions.Objective 2a. OTC impacts on the Ca. Liberibacter asiaticus (CLas) vector: Does OTC reduce pathogen acquisition by Asian citrus psyllid (ACP) adults or nymphs on infected trees?Objective 3. Assess the economic feasibility of IPC and OTC combined use.Objective 4. Disseminate project findings to citrus industry stakeholders through extension programing.
Project Methods
There will be two field trials with a factorial design of the combination of when the individual protective covers (IPC) are removed (12, 18, or 24 months) and when after the IPCs are removed the trees are injected with oxytetracycline (OTC; never, at removal, 6 months, 12 months). The two control treatments will not be covered with IPCs and one control will be injected shortly after planting. This will be done with newly planted trees. We will evaluate the titer of C. Liberibacter asiaticus (CLas) and what proportion of the titer is actively replicating as a corollary for whether the bacterium is alive. The trees will be evaluated for HLB symptoms, tree growth, root density, canopy density, and psyllid population levels. Other pest and disease pressures will be monitored. We will also evaluate phytotoxity and trunk damage; some trees will be uprooted to evaluate root density and trunk crossections for damage near the end of the project. We will also harvest the trees in the third year for one site and evaluate the total soluble solids, acid, ratio, juice color, and fruit size.Most data will be analyzed using generalized linear mixed models. The distribution used will depend on the underlying distribution of the data. Data with rating scales will either be analyzed with a categorical data analysis or a non-parametric method like relative marginal effects (Shah and Madden, 2004). The output will be interpreted by means separation. We will be analyzing for the main effects and the interactions among them.An economic analysis will be conducted where detailed cost analyses will be conducted and production practices evaluated for costs. Revenues will be projected as the trees will not reach full productivity in the duration of this project. There will also be a risk analysis of the adoption of the combined IPC and OTC treatments.We will produce extension documents, help revise current documents where appropriate, and present findings at field days. We will also have an in-service training for extension agents. Knowledge gain will be measured by pre and post tests and extension surveys during events. It is unlikely that behavior change will be measurable in the time frame of this project.?Project yearObjectiveActivityOutcome11,2Lay out plots SWFREC site, start experiment and data collectionData collected, preliminary interpretations, potential modifications to procedures at CREC site11,2Purchase trees, lay out plots CRECExperiment ready to start11-4Advisory committee meetings biannually (possibly quarterly in first year if needed)Update to advisors, use feedback to modify activities if needed13Preliminary data collectionPreparing to start analysis21,2Continue experimental activities SWFRECData collected, preliminary interpretations21,2Plant and start experiment CREC, data collectionData collected, preliminary interpretations23Develop costs associated with management activities from experiment, preliminary analysisInitial cost estimates associated with practices24Two field days and presentations to growers about preliminary results, trade show displaysGet preliminary data to growers to consider for their management plans21-4Advisory committee meetings biannuallyUpdate to advisors, use feedback to modify activities if needed31,2Continue experimental activities SWFREC including harvestWrap up experimental activities and data collection. Final data analysis31,2Continue experimental activities CRECWrap up experimental activities and data collection. Final data analysis32aExperiment set up and completed within season at CREC siteLearn whether OTC affects acquisition and transmission of CLas by ACP33Finalize economic analysisGive growers cost assessment of management practices34Two field days and presentations to growers about results, trade show displays, extension bulletins and other written documentsGet data to growers to consider for their management plans including costs31-4Advisory committee meetings biannuallyUpdate to advisors, get final feedback on results