1. Please state project objectives and what work was done this quarter to address them:
Objective 1: Determine effects of lowered soil pH on CLas populations and root physiology including internal root apoplast and vascular tissue pH.
We got our experiment in rhizotrons completed in September 2023. Sample processing and data analysis is under way. Root tracing and quantification of root traits will be completed in the next quarter. We should get the data processed and published in the next quarter or immediately following project completion.
Objective 2: Field test multiple acidification materials including organic acids for tree response CLas suppression, nutrient uptake, and root and vascular pH changes. In this quarter, we continued root sampling and soil pH determinations and applied final round of the treatments. We also finalized canopy determinatiions for trees used for the study.
2. Please state what work is anticipated for next quarter:
We will collect fruit yield and juice quality data in March/April 2024 to finalize objective 2 milestones.
We will get one article prepared and published in a refereed journal.
3. Please state budget status (underspend or overspend, and why):
The budget is on track and meeting the project milestones.
1. Please state project objectives and what work was done this quarter to address them: Objective 1: To compare different rates and annual use patterns of trunk-injected OTC on late-season (Valencia) and early-season (Hamlin) sweet orange tree and their effects on health, yield, and fruit quality over a period of 3 years in a commercial citrus production environment.Trees were harvested and fruit quality was assed in December 2023. We measured less fruit drop and increased yields (18-32%) for injected trees compared with non-injected trees, but yield differences were only significant at p = 0.12. In general, the highest OTC rate (1.65 g/tree) and the 75% rate (0.825 g/tree) resulted in the highest yield (32% increase). The highest pound solids and percent juice were measured for the trees that received the highest rate (p < 0.001). Please note that the highest rate (1.65 g/tree) was administerd by split-injections (0.825 g each on two opposite sides of the trunk). Fruit size and juice color were also improved by the injections. A subset of fruits was collected and processed for OTC residue analysis by the National Science Lab in Gastonia.Leaves were collected for CLas analysis (in progress) and tree ratings were performed. Trees that received the highest OTC rate are the densest and show the least foliar HLB symptoms compared with the controls. Obective 2: To compare spring with late summer injections in Valencia orange trees to determine if OTC effects on yield can be enhanced, and the harvest window extended, through timing of injections.Canopy ratings were performed and fruit drop was monitored. Injected trees look denser; trees that received the highest OTC rate are the densest and healthiest looking trees. 2. Please state what work is anticipated for next quarter: The Valencia trial will be harvested, fruit will be collected for fruit quality assessment and OTC residue analysis. Tentative harvest time is March 2024. 3. Please state budget status (underspend or overspend, and why):The budget is as expected.
1. Please state project objectives and what work was done this quarter to address them: Specific objectives are: 1) To determine the right timing for Zn and K treatments to minimize fruit drop.Harvest in Hamlin was done in early January. As a reminder, just like last year we performed treatments at three different dates: on early June 2023, a second set of treatments by the end of July, 2023, and a third set by early September 2023.Yields from plots treated with Zn and Zn+K in September were significantly higher than non-treated controls. Our yield numbers were 165 boxes/ acre in nontreatted controls, 224 boxes/ acre in Zn-treated trees, and 275 boxes/ acre in Zn+K treated trees. These differences were statistically significant at p<0.05. 2) To determine effects of GA3 and 2,4D applications on fruit retention when applied at different times during fruit development.This quarter we harvested the Hamlin block, unfortunately we did not see any significant differences, although GA and 2,4 D both had about 20 lb/tree more fruit (equivalent to 300 boxes per acre versus 265 boxes per acre in control), showing a positive increase trend. The block was harvested on November 20 by the grower, which we believe is exceptionally early. Therefore, any benefits that GA and 2,4 D may have on fruit drop reduction were not observed as the grower picked the fruit before fruit drop accelerates. Currently, we continue to monitor Valencia trial, we anticipate harvesting it in March 2024. 3) To develop a strong and proactive outreach program. - Alferez F. Terapias nutricionales para incrementar la producción de citricos cultivados en condiciones endémicas de HLB (nutritional therapies to increase citrus fruit yield under endemic HLB). International IST (Consultoria y Capacitacion, University of Tamaulipas, Mexico, On Zoom). November 10, 2023. 2. Please state what work is anticipated for next quarter: Harvesting of Valencia will be performed in March for both objectives 3. Please state budget status (underspend or overspend, and why): Budget continues on track
1. Please state project objectives and what work was done this quarter to address them: 1. To determine how many leaf nutrient sampling per year are required to effectively capture the tree nutritional statusand adjust fertilizer accordingly.2. To establish the relationship of leaf nutrient concentration with yield, fruit drop, and canopy density3. To determine how the leaf nutrient (all 14 nutrient) levels change in the tree throughout the year.4. To evaluate how the leaf age affects the leaf nutrient status. In this quarter we harvested the hamlin tree, monitored fruit drop, final leaf sampling was done for nutrient analysis and leaf characteristics documentation. Other activities included data analysis as we have a massive data set. The results from nutrient profile comparison of fruting and non fruiting branch show that fruting branch have severe deficiency of macro nutients as the fruit matures whereas the micronutrient depletes in non fruiting branch as the season progresses. Thus, we have initiated a small scale trial to fertilize the trees based fertilizing trees on nutrient levels in fruiting branch versus non fruiting branch. It is intersting to find that in many countries across the world, nutrient analysis is performed on fruiting branch as the growing fruit is major sink of nutrients. Thus, we believe it is imporatnt for FLorida citrus industry to know if fertilizing based on nutrients in fruiting leaf can benefit fruit production on HLB-affected trees. 2. Please state what work is anticipated for next quarter: 1. Data analysis and interpretation 2. Developing recomendations for nutrient analysis 3. Please state budget status (underspend or overspend, and why): The budget is being spent as per the plan where major funds have been used for nutrient anlaysis.We have also been able to hire staff for proper analysis and interpretation of data. 4. Please show all potential commercialization products resulting from this research, and the status of each: Changes in leaf sampling recommedation will happen as a result of this research. We anticipate to have recommendations by december 2024 including whether to sample fruting or non fruting leaves.
Soil samples were taken on November 27 and the majority of IPCs removed due to tree size. Leaf samples were collected from all trees and sent to SWREC for HLB determination (pending), trunk diameters and tree heights were measured. Nematodes and fibrous roots were recovered from the soil samples. The IPCs increased (P<0.001) the fibrous root weight more than two-fold (0.115 vs 0.055 mg/g soil), the 12-month growth of trunk girth by 81% (662 vs 365 cm3) and 12-month increase of tree height by 3-fold (19.8 vs 6.5 inches) compared to non-covered trees. Vydate had no significant effects on the tree growth in 2023 although root weights were 20% and 14% greater, and trunk girths 7% and 6% greater in IPC vs non-covered trees, respectively. To date, the cumulative sting nematodes were reduced by just 30% during this trial which is not typical of other reports of trials we have conducted. A difference between this and previous trials is that we generally apply Vydate to trees in small plots using handheld sprayers or herbicide applicators. Here, the material is injected into dedicated irrigation lines and distributed via microjets. In October we tested the hypothesis that the distribution of chemicals applied via microjet is significantly less uniform than if sprayed directly on soil. Sodium bromide was applied under 3 trees via micro-jets and soil collected at different depths and distances from the emitters, immediately and periodically for one week. The bromide was leached from the soil samples and measured. Analysis of the chemical distribution is ongoing, but a second trial measuring the deposition of water and entomopathogenic nematodes (EPN) in the wetted zone during a one-hour irrigation period is informative (Figure 1; see MS Word document). The water/EPN deposition was measured by placing canisters at different distances and directions from the emitters on several trees. Soil at distances of 1 or 5 feet from the emitter received 75% less water than at 3 feet. The deposition of EPN was even more skewed than that of water because (as with chemicals) they were injected during about 15 minutes of the hourlong irrigation cycle and had less opportunity to recover from wind directional changes. These plots were partially covered by tenting plastic sheeting over the trees; the variability would be more extreme in an open field. The data suggest that there is greater opportunity for nematodes to avoid encountering a fatal dose of the nematicide in soil treated with micro-sprinklers than with a directed spray pattern from equipment such as herbicide applicators. The project continues and will evaluate effects of water pressure and emitter configuration on the deposition patterns. The effects of the Syngenta product were also measured during this quarter. The overall suppression of sting nematodes was unaffected by an adjuvant and so the treatments with and without adjuvant were combined for analysis. When the high and low rates were applied once annually in the spring, sting nematode cumulative density during two years was reduced by 55% and 36%, respectively, compared to controls, but the differences were not significant. When the high rate was applied twice annually (in spring and fall), the sting nematodes were significantly reduced by 74%. Again, the Vydate reduction (37%) was not significant.
1. Please state project objectives and what work was done this quarter to address them: The overall goal of the project is to develop fertilization strategies to best match nutrient supply and demand, and develop recommendations for optimal nutrient application timing as compared to a simple constant supply, which will improve fruit yield, quality, and reduce fruit drop. A)Objective 1) Test if a reduced N-P-K nutrient supply in the fall is safe for sustaining HLB-affected citrus, and whether it can improve fruit quality to facilitate earlier maturity / harvesting and reduce fruit drop:Trunk diameter, fruit growth, fruit drop measurement was done in Hamlin and Valencia during October to December. Additionally, routine leaf sampling was accomplished during October and December for leaf nutrient analysis. In the 2nd week of November, treatment-wise fruit was harvested from the Hamlin variety for yield data, fruit drop % calculation, and fruit quality measurement. Temporal treatment responses on different variables and results recorded during October to December were presented and interpreted below.1. Trunk Growth: There were no significant treatment differences on relative growth rate of trunk diameter (mm/cm/month) in both Hamlin and Valencia varieties during October to December 2023. However, overall trunk growth rate in approximately in two years of the experiment was significantly higher in Valencia variety in treatment T8 and T9 (fertilizer applied 125% RDF (recommended dose of fertilizers) with 100% in spring and 25% fall season).2. Fruit relative growth rate (RGR): Fruit diameter of tagged fruit was measured every two weeks to calculate the relative growth rate of fruit after physiological fruit drop in May in both varieties. In both years, fruit RGR was not significant after August in Hamlin and Valencia. Overall fruit RGR (mm/cm/month) was also statistically non-significant between treatments in both varieties in both years.3. Fruit drop: Fruit drop was extremely high, and started after physiological fruit drop in May. We counted dropped fruit every two-week intervals in both varieties. Treatment 6 (50% fertilization in August), Treatment 8 (125% fertilization in spring and 25% in August) and Treatment 2 ( linear fertilization with 25% in August) resulted in a higher numbers of cumulative number of fruit drop per tree in Hamlin in 2023. However, only Treatment 2 showed higher fruit drop in Valencia. Fruit drop percentage was calculated based on number of fruit harvested and number of fruit drops before fruit harvesting. In 2023, only 3 replications were used for calculation in Hamlin because the 4th replication was heavily affected by citrus canker in addition to HLB disease. The fruit drop rate was higher than 70% in all fertilization treatments which were not statistically significant between treatments in Hamlin variety.4. Fruit quality at harvest:a. Fruit size (diameter and weight): After harvesting, 10 fruits were selected to measure the fruit diameter and fruit wt. There was no treatment effects on fruit diameter and single fruit weight in Hamlin variety in 2023. b. Juice quality: The fertilization treatment did not affect the juice quality of Hamlin fruit. Total soluble solids (TSS), titratable acidity (TA), and TSS:TA ratio were NS. c. Fruit yield over time: Yield was very low in Hamlin due to perhaps severe HLB infestation and excessive fruit drop. The projected potential yield of these trees was only 153 boxes/acre if no fruit drops had occurred. However cumulative excessive fruit drop resulted in very low fruit retention and less fruit yield. Treatment 10 resulted in a higher yield (~58 boxes/acre) than other treatments which was still not likely profitable. Objective 2) Develop an optimized, practical fertilizer timing management profile to boost fruit quality and reduce fruit drop for HLB-affected citrus based in part on the sigmoidal nutrient demand curve defined by four physiological growth phases (0=bloom/fruit set; 1=cell division; 2=cell enlargement; 3=maturation):Due to the absence of significant differences to date, we have not made progress with this objective. The hurricanes of 2022 caused damage that takes years to repair, and the constant high pressure of citrus canker on the Hamlin trees in particular has been an additional source of noise that masks any treatment response.B) New developments: NoneC) Issues: None, except those mentioned above that are beyond our control.2. Please state what work is anticipated for next quarter:Routine lysimeter sampling, leaf sampling, processing and analysis will be ongoing, as will tree size, root growth and fruit drop and growth measurement.Plan for January to March:1. Sampling for leaf nutrient analysis2. Fruit diameter measurement (Valencia)3. Collection of leachates for nitrate N loss and analysis4. Scanning of the Minirhizotron for root growth5. Fruit drop count in every two weeks until harvesting in Valencia6. Harvesting Valencia variety for yield and fruit quality measurement 3. Please state budget status (underspend or overspend, and why):Spending rate is slightly below the target by about 10%. This is considered within the normal deviations of budgeting.
1. Please state project objectives and what work was done this quarter to address them:In the first quarter of the agreement, the CRAFT Foundation accepted applications for Round Two of the Existing Tree Therapies program as well as Cycle Five of the tradtional CRAFT new planting program. After review by CRAFT staff to validate the eligibility of applications, the CRAFT Board of Directors voted to approve all eligible Existing Tree Therapies applications submitted in Round Two, including those rolled over from the Round One waitlist. A total of approximately 920 projects were approved. Approximations are due to consolidation of applications, which may require some revision prior to final execution of agreements. These projects include acreage from all major citrus-growing regions in the state, as well as varieties including oranges, grapefruit, hybrids and others. While the majority of projects are focusing on the injection of oxytetracycline, treatments of giberellic acid, 2,4-D and brassinosteroids are also included in the approved projects. The Round Two approved projects combine with those previously approved in Round One for a total of more than 1,100 Existing Tree Therapies projects representing approximately 74,000 acres. Participation Agreements were sent to growers in December and are to be returned by January 31, 2024 unless otherwise approved by CRAFT. Participants from both Rounds One and Two have begun submitting their three-year historical data to CRAFT. This data will be added to the CRAFT Data Portal moving forward. To-date, 97 percent of Round One projects and 36 percent of Round Two projects have submitted their historical data. Cycle Five of the traditional new planting program received 175 new applications. An additional 46 applications rolled over from the Cycle Four waitlist for consideration in this cycle as well. A total of 211 applications representing more than 14,000 acres will be reviewed and considered for approval by the CRAFT Technical Working Group and Board of Directors. Based upon the projects presented, applications were organized by solid-set and reset and further within subgroups of similar projects for replication and evaluation purposes. As of January 2024 CRAFT’s Scientific Coordinator has reached out to all growers and has finalized design proposals for the majority of projects. All projects will be presented to the CRAFT Technical Working Group at their February meeting for review and discussion with the expectation of finalizing a slate of recommendations for the Board of Directors during the March TWG meeting. The final slate of projects approved by the CRAFT Board of Directors for Cycle Five will join the 226 projects representing more than 9,000 acres in Cycles One – Four. In addition to the development of projects and execution of contracts, CRAFT staff continued communications and outreach efforts including, articles in multiple industry and general publications; updating of the CRAFT website (craftfdn.org); public meetings of the Technical Working Group and Board of Directors; and more. A full list of communications efforts is available upon request. 2. Please state what work is anticipated for next quarter:The development and approval of Cycle V projects will continue, as well as the execution of ETT Round Two contracts and submittal of historical data. ETT Round One participants will also begin entering data for the harvest year 2023-24. Additionally, Cycle Four projects continue to be planted. Following completion of planting, pre-audits of each project are used to confirm the planting of trees and compliance with contract to date. Growers are expected to report production data in real time or at least quarterly in to the USDA-CRAFT Data Portal. The data portal will include a separate entry point for data/ measurements from third party partners such as FDACS and Aerobotics. Data entered by participants and third parties for each project will be visible initially by the growers for their individual projects, and at a later date, on public dashboards developed by CRAFT and USDA-ARS. 3. Please state budget status (underspend or overspend, and why):As of January 2024 contracted grower payments were in line with budget and all invoices had been submitted to CRDF.
1. Please state project objectives and what work was done this quarter to address them: Objectives: 1) Test the efficacy of different injection devices, 2) Determine the most effective formulation of OTC, 3) Determine the best month of injection and most appropriate OTC concentration based on tree size. Trial 1: SW FL(Duda) – 8-year-old Valencia/Carrizo. Trial 2: SW FL (Graves Bros) – 8-year-old Valencia/Kuharske. Trial 3: East coast (Graves Bros) – 9-year-old Valencia/sour orange. Trial 4: East coast (Graves Bros) – 4-year-old Valencia/x639. Trial 5: Central ridge (King Ranch) – 4 year-old OLL8/x630 Fruit drop, disease ratings, and tree measurements were conducted. We are continuing with PCR/CLas analyses.Selected information from these trials was presented at the MISA conference in november at UCF. The grower collaborator for trial 1 has unfortunately stopped tree care after our year 2 injections, and trees have been declining rapidly. We have therefore terminated our evaluations in this trial. 2. Please state what work is anticipated for next quarter: Fruit drop assements will continue. Tree size measurements will be conducted. Leaf samples will be collected for PCR/CLas analysis. We are preparing for the harvest. Harvest dates will be coordinated with the grower collaborators. 3. Please state budget status (underspend or overspend, and why):Although our activities are on track, a large portion of funds intended to be used for OTC analysis at the USDA National Science Lab in Gastonia, NC, and for fruit quality analysis in 2024 remains unspent because the start/end date of the grant coincides with the harves time. We have asked for a no cost extension to complete these research activities.
1. Please state project objectives and what work was done this quarter to address them:
Overall goal and specific objectives. The overall goal in this proposal is to evaluate the utility of trunk-injected OTC for reducing CLas infection and transmission in non-bearing and bearing citrus. The specific objectives are to:
Objective 1) Quantify CLas reduction and tree health in response to OTC.
Experiment 1.1. Mature Trees. Field trials were established with grower collaborators in groves at Wauchula and Frostproof, Florida.
For the Wauchula grove, treatments were applied to 10-year-old, CLas-infected Valencia trees of a standard size and CLas titer. Four treatments under evaluation are: 1) insecticide control of ACP on productive trees, 2) insecticides plus addition of trunk injection of OTC on productive trees, 3) insecticides control of ACP on non-productive trees, and 4) insecticides plus addition of trunk injection of OTC on non-productive trees. The insecticide treatment consists of a program that is intended to represent what certain growers are doing currently4-6 annual sprays of formulations labeled for ACP that are rotated between the following active ingredients: (thiamethoxam, imidacloprid, spinosyn, fenpropathrin, cyantraniliprole, methoxyfenozide, clothianidin, and diflubenzuron). Rectify was injected into mature trees at 50-100mL/tree (8250 ppm solution), according to the product label, in April 2023 using tree injectors. Each treatment was applied to four replicate groups of 0.022 ha plots that consisted of four rows, with five trees/row comprising 20 trees per plot.
Treatments at the Frostproof site were applied to 10-year-old, CLas-infected Valencia or Hamlin trees of a standard size and CLas titer. Four treatments are being evaluated: 1) insecticide control of ACP on Valencia trees, 2) insecticides + addition of trunk injection of OTC (Rectify) on Valencia trees, 3) insecticide control of ACP Hamlin trees, and 4) insecticides + addition of trunk injection of OTC (ReMedium) on Hamlin trees. The insecticide treatment consisted of a program that is intended to represent what many growers are doing currently4-6 annual sprays of formulations labeled for ACP and were rotated between the following active ingredients: (thiamethoxam, imidacloprid, spinosyn, fenpropathrin, cyantraniliprole, methoxyfenozide, clothianidin, and diflubenzuron). Rectify was injected into mature trees at 50-100mL/tree (8250 ppm solution), according to the product label, in March 2023 using tree injectors. Each treatment was applied to four replicate groups of 0.022 ha plots consisting of four rows, with five trees/row comprising 20 trees per plot. According to the product label, using tree injectors, Oxytetracycline (ReMedium) was injected into mature trees at 50-100 mL/tree (5,500 ppm solution) in March 2023. Each treatment was applied to four replicate groups of 0.022 ha plots that consisted of four rows, with five trees/row comprising 20 trees per plot.
Tree Infection Sampling. Monthly leaf samples are harvested from all treatment plots in both experiments. Four mature leaves are randomly selected from five trees in the second row of each replicate plot at each sample date to assess CLas infection. Collected leaves were placed into plastic bags in the field and transported to the laboratory in coolers with ice, where they were stored at -20oC for subsequent CLas detection, as described below.
Detection of CLas in plants and psyllids. Dual-labeled probes were used to detect CLas in ACP and citrus plants using an ABI 7500 qPCR system (Applied Biosystems, Foster City, CA) in a multiplex TaqMan qPCR assay described in (Li et al. 2006). DNA from insect and plant samples was isolated using the DNeasy blood and tissue or DNeasy plant kits (Qiagen Inc, Valencia, CA), respectively. Las-specific 16S rDNA from psyllid and plant extracts were amplified using probe-primer sets targeting internal control sequences specific to ACP [insect wingless] or plant [cytochrome oxidase] gene regions (Li et al. 2006). DNA amplifications were conducted in 96-well MicroAmp reaction plates (Applied Biosystems). Quantitative PCR reactions consisted of an initial denaturation step of 95°C for 10 min followed by 40 cycles of 95°C for 15 s and 60 °C for 60s. Each 96-well plate containing ACP samples included a no template control, a positive control (Las DNA in DNA extractions from ACP), and a negative control (no Las DNA in DNA extractions from ACP).
Tree health. Tree growth was assessed at the beginning of experiments to determine the effect of OTC injection over time at both locations. Tree size measurements (height, canopy, width, and trunk diameter at tree base) are taken from each tree in each treatment replicate. The measurements have been made at the initiation and mid-way through the experiment, and will also be made at the end of study. New leaf growth (flush) is being assessed monthly during the growing season by quantifying the number of flushes in an open 0.3m3 cube placed into three random positions per five trees of each replicate (Hall and Albrigo 2007).
Recent activities:
Leaf samples corresponding to May through December 2023 were successfully collected at both locations and are currently being processed for CLas detection. Additionally, flush numbers were successfully collected. Tree health measurements were done at time zero and in the middle of the experiment at both locations. This report presents results regarding CLas infections obtained from May to August 2023 in both locations.
Wauchula site. At this field site, we are investigating whether application of Rectify could stop tree decline and improve the productivity of tree in severe decline in commercial groves. In May 2023, a month after injections were applied to trees, a decrease in CLas abundance occurred in injected unproductive and productive trees compared to their respective control treatments. In June 2023, injected productive trees exhibited significantly lower CLas abundance than the control. In July and August 2023, significantly lower CLas abundance was observed on injected unproductive trees, followed by injected productive trees as compared with their respective controls. Overall, trees injected with Rectify showed lower CLas abundance than their respective controls, with statistically significant reductions in bacterial titer observed 60 days after injection.
Frostproof site. At this field site, we are comparing the efficacy of two OTC formulations (Rectify and Remedium) in reducing CLas infection in commercial groves. In May 2023, two months after injections were applied, trees injected with Rectify had lower CLas abundance than those injected with Remedium. This trend continued in June and July. However, CLas abundance was statistically lower in Rectify-treated trees during these two comnths compared with their respective controls, which pathogen titer was not statistically reduced in Remedium-treated trees compared with controls. In August 2023, there was lower CLas abundance observed in Rectify or Remedium-treated trees than in controls. Overall, Rectify-treated trees had the lowest CLas abundance among treatments 60 days after injection and this result remained consistent throughout the summer of 2023. In general with both formulations, OTC-injected trees had lower CLas abundance in all cases than not-injected trees.
Objective 2) Determine the effect of OTC injection on psyllid populations.
Psyllid Population Sampling. On each sampling date and each location, Asian citrus psyllid (ACP) adults were sampled in all plots by placing a 22 × 28 cm white plastic sheet horizontally and 30 cm underneath a randomly chosen branch. Each branch was struck three times with a 40 cm length of PVC pipe. Adult ACPs falling onto the sheet were quickly counted (Monzo et al. 2015). All trees in the replicate were sampled in this manner each month.
Recent activities:
ACP adult populations have been monitored monthly from May through December 2023 at both locations. During the next reporting period, we will include results regarding the effect of OTC on ACP adult populations.
Objective 3) Determine the effect of OTC injection on CLas transmission.
Field trials were established at a collaborator grove at Babson Park, Florida. In this grove, treatments were applied to 10-year-old, CLas-infected Valencia trees of a standard size and CLas titer. There were four treatments evaluated: 1) Rectify (8,220 ppm), 2) Remedium (5,500 ppm), 3) Fireline (70,000 ppm) (positive control), and 4) Insecticides only (negative control). For all antibiotics, trunk injections were performed using Chemjets. In this location, CLas infection in trees was evaluated by randomly collecting four leaves at time zero, 2, 7, 30, 45, 60, and 90 days after injection. Additionally, 40 leaves per tree (20 top and 20 bottom) were collected from 2 trees in each replicate plot to measure the translocation of treatments at the times mentioned above.
Experiment 3.1. Acquisition assays. Psyllid nymphs, which develop on immature leaf tissue, acquire CLas more efficiently than adults; therefore, acquisition of CLas from OTC-treated infected citrus trees was compared with acquisition from untreated infected trees, using the abovementioned treatments. ACP adults (five female and five male) from uninfected laboratory cultures were on young leaf growth (flush) of treated or control infected trees for oviposition. Each treatment was replicated three times on individual trees. Following oviposition, adults were collected and preserved for CLas detection. Egg clutches were left on trees enclosed in mesh sleeves. After nymphs reached adulthood, psyllids and leaves from test plants were collected. Transmission assays were repeated on the same trees every four months following treatments to determine the influence of treatments on pathogen acquisition over time. The effect of OTC injection on the acquisition of CLas was assessed by comparing the CLas titer in ACP caged on citrus trees before and after treatments and across time.
Experiment 3.2. Inoculation assays. A subsample of 10 ACP per treatment collected from the above trees was transferred to uninfected citrus seedlings in an insect-proof greenhouse. ACP was enclosed on plants for inoculation feeding for 7d. After that, ACP adults were collected for CLas detection using RT-PCR. Furthermore, leaves will be collected every 30, 45, 60, 90, 120, 150, and 180 days for CLas detection.
Recent activities:
.Leaves were collected to measure both CLas infection and OTC translocation and are currently being processed. The first replication of sampling for experiments 3.1 and 3.2 was successfully completed in June 2023. A second replication was performed in August for all experiments. The upcoming report will include results regarding the effectiveness of OTC formulations on CLas transmission (CLas acquisition and inoculation) and OTC translocation. This report presents results regarding the effects of OTC treatment on CLas transmission by ACP during the priod from initiation of the experiment (day 0) to 90 days after injections.
Babson Park field site. At time zero, CLas infection levels were similar across treatments. Two and seven days after treatments were applied, CLas abundance fluctuated across treatments, and no statistical differences were observed. At 30 days after treatments were applied, trees injected with Fireline exhibited the lowest CLas abundance, followed by Rectify and Remedium treated trees and then the control. At 30 days after treatment, CLas abundance was statistically lower in Fireline or Rectify-treated trees than that observed in control trees. After 45 days, Fireline-treated trees showed significantly lower CLas abundance than the other treatments tested, and no statistical differences were observed between pathogen load in trees treated with Rectify and Remedium as compared with control trees. At 60 days after treatments, the lowest CLas abundance was observed in Remedium-treated trees, followed by Fireline and then Rectify-treated trees. However, these reductions in CLas abundance were not statistically different from the control. A similar pattern was observed at 90 days after treatments were applied, but the highest CLas abundance among treatments was observed in Rectify treated trees. Overall, Fireline-treated trees exhibited the lowest CLas abundance across time, followed by Remedium-treated trees.
2. Please state what work is anticipated for next quarter:
This investigation is ongoing. TWe are currently wrapping up the initial field season for the project and have harvested fruit for analysis. Fruit/juice quality data will be reported next quarter.
3. Please state budget status (underspend or overspend, and why):
The budget spending is on track as anticipated.
4. Please show all potential commercialization products resulting from this research, and the status of each:
Not applicable at this time. This project is evaluating registered and available products.
1. Please state project objectives and what work was done this quarter to address them: Specific objectives are:1) To determine the right timing for Zn and K treatments to minimize fruit drop.2) To determine effects of GA3 and 2,4D applications on fruit retention when applied at different times during fruit development.3) To develop a strong and proactive outreach program. For objective 1 we did a new set of treatments by the end of September in Hamlin as we did last year. This date of treatment was the one that got best results last season in terms of yield, despite the effects of hurricane Ian. As before, every set of treatments is performed in an independent replicated block, so treatments are applied only once, to assess the best timing to achieve the best results. Trees under Zn and Zn+K treatments continue having greener canopies. This is consistent with effects we saw last year. Also, we are performing canopy analysis by using the ImageJ program. In Hamlin, trees treated with Zn continue to have significantly more dense canopies and more canopy volume than controls. These measurements have been done also for objective 2, and we are analyzing data. For objectives 1 and 2 we are also analizyng foliar nutrient concentrations.We see less oxidative stress levels in trees treated with Zn and Zn+K.Fruit drop is being now monitoired weekly. We still don’t see differences in treatments but this is usually seen in October-November. Objective 3:-Optimizing foliar sprays of zinc and potassium to prevent fruit drop, by Fernando Alferez, Daniel Boakye, Murillo De Sousa and Pablo Orozco. Citrus Industry, Tip of the Week, October 2023. 2. Please state what work is anticipated for next quarter: Treatments for objectives 1 and 2 will continue as programmed in Hamlin. We will continue fruit drop assesments weekly. Sampling will continue as well and we will finisnh data analysis of samples analyzed in the last quarter for objectives 1 and 2. Harvesting of Hamlin will be done in December-January. Treatments in Valencia will start. 3. Please state budget status (underspend or overspend, and why): Budget is on track
1. Please state project objectives and what work was done this quarter to address them: The objectives of this project are: 1, To study the effect of Brs on priming immunity on young, newly planted trees. This will allow to know for how long immune response will last after Br application, so we can adjust timing (number of applications). We have continued treatments and samplings. After 8 months (with a monthly application), most of the trees (around 60%) are still HLB-negative. Denser foliage has consolidated in a denser canopy. Fall flush was highly syncronized, following the trend we observed during Summer flush. 90% of the trees treated with Brs achjieved fully expanded leaf status at the same time. This happened only in 20% of non-treated trees. This indicates that flushing occurred at the same time in Br-treated trees, and will allow better planification of insecticide sprays. 2, To determine the best time of application (frequency) to achieve maximum protection against pests and disease in newly planted trees. Immunity is still greatly increased after 45d of treatment. We have now started plots applying Brs every 45d or 60d. We will monitor the same parameters, icluding Ct values and tree health. 3, To determine the effect of Br application on advancing fruit maturation in both Valencia and Hamlin. Treatments started in September on Hamlin. We performed two different sets of treatments: biweekly treatment and only once treatment. We are following quality every 15 days, including internal quality and external color development. So far, it is remarkable that internal maturation and quality are in general superior than last year. At the beginning of the treatments, control fruit was already at 9.38 Brix. This value was about 8.2 last season. So far we do not see a significant increase in Brix with Br treatment. This is coincident with what we saw last year, as differences started to be significant in November.Values for early November are 9 for control and 9.43 for Br-treated. However, ratio is greatly increased, 13.32 in Br-treated as compared to 11.5 in controls. External color is also increased. 2. Please state what work is anticipated for next quarter:For objectives 1 and 2 we are continuing sampling and molecular analysis.In objective 3, treatments in mature Hamlin trees are already running. We will be harvesting fruit in December-January, depending on the commercial farm schedule. Last season, harvesting was performed by January 5th. We will determine yield and fruit quality. We will start treatnments in Valencia in early January.For objectives 1 and 2 we will continue treatments, samplings and molecular analysis to determine the best timing for treatments to achieve the most protection against psyllid infestation. For objective 3, we will start in August treatments on Hamlin. We will also continue analyzing juice samples from Hamlin and start analysis on juice samples from Valencia. We have included also an injection treatment of Brs in trees, This was not in the proposal, but we believe it may have interest. We have started in October. We will be injecting once per month until harvest and measuring the same parameters as in objectives 1, 2 and 3. 3. Please state budget status (underspend or overspend, and why): Spending is on track
1. Please state project objectives and what work was done this quarter to address them: Objective 1: To compare different rates and annual use patterns of trunk-injected OTC on late-season (Valencia) and early-season (Hamlin) sweet orange tree and their effects on health, yield, and fruit quality over a period of 3 years in a commercial citrus production environment.Obective 2: To compare spring with late summer injections in Valencia orange trees to determine if OTC effects on yield can be enhanced, and the harvest window extended, through timing of injections. Trees were monitored. No phytotocicity was obserevd after the spring injections. Fall injections were conducted in September in the Valencia trial. No phytotoxicity was noted. 2. Please state what work is anticipated for next quarter: We will conduct tree measurements. Leaves will be collected for CLas assessment. In the Hamlin trial fruit will be collected for fruit quality assessment, and trees will be harvested. Tentative harvest time is middle of December. 3. Please state budget status (underspend or overspend, and why):The budget is as expected.
1. Please state project objectives and what work was done this quarter to address them: The overall goal of the project is to develop fertilization strategies to best match nutrient supply and demand, and develop recommendations for optimal nutrient application timing as compared to a simple constant supply, which will improve fruit yield, quality, and reduce fruit drop. A)Objective 1) Test if a reduced N-P-K nutrient supply in the fall is safe for sustaining HLB-affected citrus, and whether it can improve fruit quality to facilitate earlier maturity / harvesting and reduce fruit drop:Routine measurements of tree health and performance continued, including leaf nutrient analyses, chlorophyll index, canopy and trunk size, fruit growth rates and incidental fruit drop (not pre-harvest). The study comprehensively analyzed the nutrient dynamics of leaves, revealing notable variations in nitrogen (N) concentrations. During the cell-division stage / physiological fruit drop in May to the cell-enlargement stage starting June, both Hamlin and Valencia varieties exhibited higher leaf N concentrations in most fertilization treatments, except for two linear supply treatments (T1 and T2). This increase in leaf nitrogen could contribute to enhanced crop health and performance. In contrast, potassium (K) concentrations in leaves remained consistent across various fertilization treatments throughout the growing period. However, a spike in leaf K concentration was observed in both Hamlin and Valencia during the fruit maturation phase (September-), particularly in treatments with linear nutrient supply and late fertilization. This is significant given that numerous studies indicate that lower potassium levels are preferable for improved fruit quality and peel coloration. Conversely, the temporal fluctuations of other nutrients did not show significant variations across different fertilization treatments.Objective 2) Develop an optimized, practical fertilizer timing management profile to boost fruit quality and reduce fruit drop for HLB-affected citrus based in part on the sigmoidal nutrient demand curve defined by four physiological growth phases (0=bloom/fruit set; 1=cell division; 2=cell enlargement; 3=maturation):In the 2023 growing season, an increase in fruit drop was observed in both Hamlin and Valencia varieties as the season progressed. Specifically, the lowest cumulative fruit drop per tree in Hamlin was recorded under treatment 3 (100% sigmoidal fertilizer supply). On the other hand, Valencia showed a higher cumulative fruit drop per tree, particularly in the linear supply with late fertilization treatment (T2). The overall percentage of fruit drop will be determined after the harvest.Regarding fruit growth, no significant differences were observed in the relative fruit growth rate among the various fertilization treatments. B) New developments: NoneC) Issues: None2. Please state what work is anticipated for next quarter:Routine lysimeter sampling, leaf sampling, processing and analysis will be ongoing, as will tree size, root growth and fruit drop and growth measurement.Plan for October to December:1. Sampling for leaf nutrient analysis2. Fruit diameter measurement3. Collection of leachates for nitrate N loss and analysis4. Scanning of the Minirhizotron for root growth5. Fruit drop count in every two weeks till harvesting in Hamlin and Valencia6. Harvesting Hamlin variety for yield and fruit quality measurement7. Soil sample collection from Hamlin variety blockIn the Sugar Belle peel thickness experiment, all treatment allocation was completed for this year’s experiment and final harvesting will be done during December for fruit quality and peel thickness measurements. Leaf sample collection will be done after harvesting of fruits and processed for leaf nutrient concentration. 3. Please state budget status (underspend or overspend, and why):Spending rate is approximately on track.
1. Please state project objectives and what work was done this quarter to address them:
Objective 1: Determine effects of lowered soil pH on CLas populations and root physiology including internal root apoplast and vascular tissue pH.
We got our experiment in rhizotrons completed in September 2023. Sample processing and data analysis is under way.
Objective 2: Field test multiple acidification materials including organic acids for tree response CLas suppression, nutrient uptake, and root and vascular pH changes. In this quarter, we continued root sampling and soil pH determinations. We request 6-month extension because will need to collect fruit yield and juice quality data in March/April 2024.
2. Please state what work is anticipated for next quarter:
A poster on Objective 1 will be presented at the Soil Science Society of America annual meeting in St. Louis, MO.
3. Please state budget status (underspend or overspend, and why):
The budget is on track and meeting the project milestones. However, we plan to request a no-cost extension so as to collect a fourth harvest in 2024 and also owing to some delays we had in executing the greenhouse portion of the project due to changes in project leadership.
1. Please state project objectives and what work was done this quarter to address them: Objectives: 1) Test the efficacy of different injection devices, 2) Determine the most effective formulation of OTC, 3) Determine the best month of injection and most appropriate OTC concentration based on tree size. Trial 1: SW FL(Duda) – 8-year-old Valencia/Carrizo. Trial 2: SW FL (Graves Bros) – 8-year-old Valencia/Kuharske. Trial 3: East coast (Graves Bros) – 9-year-old Valencia/sour orange. Trial 4: East coast (Graves Bros) – 4-year-old Valencia/x639. Trial 5: Central ridge (King Ranch) – 4 year-old OLL8/x630 Leaf CLas detection analyses are in progress. Leaves were collected for nutrient analysis (in progress). Trunk injury/wounding was assessed in each trial. August and September injections were conducted in trials 4 and 5. September injections were conducted in trial 1. Selected information from these trials was presented at several industry events and conferences, including the Citrus Expo, Packinghouse Day, ASHS, and the International Citrus and Beverage Conference. Research findings were also disseminated in Citrus Industry magazine and through the UF/IFAS citrus podcast. 2. Please state what work is anticipated for next quarter:We will conduct tree size measurements. CLas titer analysis will continue. Fruit drop and tree health will be monitored. 3. Please state budget status (underspend or overspend, and why):The budget is on track although it may appear to be underspent as a large portion of funds are intended to be used for fruit OTC analysis at the USDA National Science Lab in Gastonia, NC, and for fruit quality analysis in 2024.
(863) 956-8817
(863) 956-5894
700 Experiment Station Road
Lake Alfred, FL 33850
Email Us
