July 2015 The objectives of this proposal are 1) to determine if a) leaf litter biodegradation treatments reduce Guignardia spp. pseudothecia and improve control afforded by routine fungicide applications; b) if biodegradation is affected by the current fungicide application practices; and c) whether the biodegradation treatments will affect current citrus best management practices (BMP); 2) to determine the seasonal dynamics of leaf litter inoculum load in varying management regime intensities and how environment affects pseudothecia production in the leaf litter; 3) to test if the resistance to black spot in the leaves and fruit in sour orange is correlated and under simple genetic control through laboratory and field testing of progeny of sour orange crosses in both Florida and Australia. In the large field trial, there was ten times more G. mangiferae than G. citricarpa in the leaf litter. In 2014, there was no pattern in the number of leaves with Guignardia structures over time in any treatment. The treatment with the greatest number of leaves with structures was urea over all. In 2015, the pattern of structure formation was consistent across treatments and over all the treatment with the fewest structures was urea. The DNA analysis of the 2015 leaf litter has not yet been completed. The bagasse field trials confirmed the laboratory experiments that bagasse increased the leaf decomposition rate compared to nothing or urea. Greater soil moisture also accelerate leaf decomposition. The manuscript preparation continues. From April 13th to July 30th, nine batches of samples of citrus leaf litter were routinely collected from orchard near Immokalee. Each batch of samples contains 40 samples of 25 leaves collected below 40 trees. Leaves were examined under microscope to check for fructification of Phyllosticta spp. Leaf portions without fructification were discarded and the remainder were immersed in 0.02% tween20 to collect conidia and ascospores. Conidia and ascospores produced in leaf litter were quantified, weather data were collected from FAWN. These new data will be combined with the other data to analyze the seasonal dynamics of Phyllosticta spp. spores. In Australia, work continues on the mating and production of ascospores for Phyllosticta on leaf disks in culture. After 6 months they are still under observation. No inhibition is seen between isolates unlike on culture media. There is good growth of asexual structures. Inoculated fruit are still under observation in the field. Some accessions have started to mature and so far the results are as expected with sweet orange related fruit but many relatives have not reached maturity yet. They are repeating the fungicide work to confirm previous results.
July 2015 The objectives of this proposal are 1) Determine the base line level of Guignardia citricarpa sensitivity to fungicides registered for disease control in citrus and evaluate new products for efficacy against G. citricarpa in vitro; 2) Conduct and improve implementation of spray trials for efficacy of registered products for citrus and to evaluate novel compounds in the field; 3) Optimize field evaluation of control measures through analysis of the spatiotemporal disease progress utilizing past and current field data of the outbreaks to gain knowledge on the incidence, severity and rate of the epidemic and assess the fungal population to increase the likelihood of successful field research and 4) Evaluate products and treatment conditions for postharvest control of citrus black spot. This quarter we accomplished: Objective 1: Manuscript preparation continues for the DMI fungicides. Assays with SDHI’s are continuing and different media are being evaluated for best functionality. Experiments with Cannonball and Vanguard are continuing. Most of the mycelial tests are complete and spore germination assays are underway. Objective 2: Fungicide trials were initiated in May 2014 and completed March 2015. Thirteen different fungicide regimes utilizing eight materials, both registered and experimental, were evaluated for their effectiveness in suppressing CBS. Fruit were assessed on the tree for the proportion of symptomatic fruit as well as the proportion of symptomatic fruit on the ground. Several fungicides regimes showed significant differences at one or more rating and results from this and previous trials are being used for product label expansion for CBS. Objective 3: Sites were re-mapped in December 2014 to assess changes (trees pulled and/or re-planted) between the 2013-2014 and 2014-2015 citrus seasons. Trees were mapped for the presence or absence of CBS in two Valencia groves. Positive trees were defined as having fruit with at least a single hard spot lesion. The hard spot lesion was chosen due to its ease of recognition as a symptom of CBS. Data for CBS were collected from both groves between December 12th 2014 and April 16th 2015. Grove I consisted of 2144 trees (22 rows x 103 tree spaces; 122 spaces open). Eighty trees were positive for CBS (3.7%). Grove II consisted of 4347 trees (36 rows x 127 tree spaces; 225 spaces open). Seventeen percent (739/4347) were positive for CBS. The binomial dispersion index (D), revealed clustering of symptomatic trees for both groves in all quadrant sizes tested. Monte Carlo simulations for the L function in R confirmed CBS aggregation for both groves. Monitoring will continue through the 2015-2016 citrus season. Objective 4: Fruit quality measurements were made on fruit tested with carvacol and thymol. Peel injury was noted with both treatments but especially for thymol.
The overall objective of this project is to investigate the feeding deterrence provided by reflective colored kaolin clays on citrus plants from Asian Citrus Psyllid (ACP). Kaolin clay product is an EPA approved pesticide and currently employed for crop protection in apples, pears, melons and citrus. Most of the studies in this project have been performed with kaolin clays including Surround kaolin clays product. Colored kaolin clays were developed using select dyes, including FDA certified colorants approved for agricultural use by the EPA (list 180.920), covering the range of visible spectrum. Surface modifications were performed with surfactants and polymers to adsorb dyes on clay surfaces. Methods were further developed to minimize the leaching of the dyes from the particles. Ten different colored clays were developed with reflectance in the visible region with dyes e.g. FD&C Blue 1, FD&C Red 40, Basic Blue 54, Crystal Violet, and FD&C Yellow 6, D&C Violet 2 etc. The optical properties of the clays were determined by total reflectance and colorant strength measurements. Reflectance measurements showed that each material has an altered absorption peak and reflectance not exhibited by the unmodified clay. Particle size distribution and zeta potential measurements were also performed to determine the physical characteristics of the suspensions. While the zeta potential of the unmodified kaolin clay was found to be negative, the surface modifications and doping of clay material with the dyes, led to significant changes in the zeta potential. The effect of colored clay coatings on photosynthesis was measured in leaves of selected citrus plants with a LiCOR 6400 gas exchange system under greenhouse conditions. While four kaolin coatings showed higher mean photosynthetic values and four lower, as compared to unmodified Surround clay. The decrease in the photosynthesis due to coatings is expected since they change the reflectance of the leaves. However, as compared to greenhouse, field grown trees are often light saturated and white Surround clay coated trees have shown higher photosynthesis rates in field. One of the limitations of the particle film technology has been the wash-off due to rainfall. Preliminary studies were performed to improve the rain fastness tests using commonly used stickers, binders and viscosity modifiers. Adjuvants such as Kollicoat (dispersion of poly vinyl acetate) and polymer adjuvant (sodium poly acrylate) showed improvement in rain fastness, withstanding up to 5-7 cm rainfall. Further studies are required to determine adjuvants that can increase the adhesion of the kaolin clays to withstand up to 15 cm rainfall. The ability of the colored clay coatings to adequately coat a leaf surface and alter preferred portions of reflected light was determined using reflectance and colorant strength measurements on citrus plants. Uncoated leaves generally had the lowest reflectance values across the visible range of photosynthetically active wavelengths. The majority of the Kaolin suspensions flattened the reflectance curve relative to uncoated leaves by increasing reflectance. Two clays FD&C Violet and Cert Green Kaolin solutions had higher reflectance values across the 400-700 nm range. Colorant strength measurements performed separately using portable spectrophotometer showed that thick coatings are effective in significantly altering the colorant strength of the leaves. For example while FD&C Red 40 and Bright red increased the red scale FD&C Blue 40 and FD&C Violet significantly increase the blue strength as compared to uncoated citrus. Dye-doped clays that significantly altered the reflection of the foliage were used for the ACP inhibition tests. In choice tests, ACP showed minimal preference for leaves coated with red colored clays as compared to uncoated and Surround clay coated plants. These results demonstrate the contribution of the visual deterrence in ACP s feeding behavior.
Canker disease on fruit and foliage is under evaluation in the following 2015 trials: 1) Canker management in grapefruit: Foliar applications of novel bactericidal formulations are compared with standard film-forming copper and zinc formulations: 1) Nordox 75WG, 2) Nordox 30/30 with 0.5 lb of metallic copper and an equivalent amount of metallic Zn, 3) Nordox 45/15 WG, 4) 2 Zinkicide formulations 5) 6 T-sol formulations; 6) CuSiNG-Quat-P (Cu+Quat), 7) Fixed-Quat DDAC, 8) CS-CuSiNP, 9) SG0025 (treatments 4-9 are experimental formulations from Dr. Swadesh Santra, a Nano-chemist at Univ. Central Florida), 10) Untreated check 2) Canker management in Hamlin: Foliar applications of standard film-forming copper formulations and soluble copper formulations are compared in 4 yr old trees 3) Greenhouse assay to evaluate local systemic and residual activity of selected UCF formulations and FireWall against Xanthomonas citri subsp. citri on potted Pineapple orange trees inoculated by injection infiltration 4) Assessment of Cu bioavailability and residual activity on grapefruit for copper oxide (Nordox 75 WG) and the copper-zinc formulation Nordox 30-30 during two periods of summer season (July and August) to test whether zinc may be enhancing the bioavailability of Cu from the copper oxide in the 30/30 formulations compared to 75 WG copper oxide alone
Report for period ending 4/30/15 (FINAL REPORT) Work continued on our previously reported efforts to determine the level of imidacloprid in leaf tissue required to prevent ACP phloem feeding behaviors. In particular we have focused efforts at measuring the levels of neonicotinoids in different parts of the leaf tissue and how that changes with time. While this work is still underway, progress to date does show uneven distribution of neonics within a leaf that changes over time. There also appears to be some difference in movement patterns between the different neonics which may be due in part to their differences in water solubility. Further work is ongoing to better characterize these movement patterns and use that information to then determine when retreatment of plants is needed in order to ensure psyllids are not able to feed successfully on treated plants. Use of EPG techniques to determine the level of imidacloprid needed to prevent phloem feeding behaviors has continued. While still ongoing, we have narrowed down the LC50/LC90 for feeding disruption and should be able to be begin work soon for the other neonicotinoid compounds. This work will be continued in the coming year to help refine the use of soil-applied nenicotinoids for protecting young trees from HLB via disruption of psyllid phloem feeding behaviors.
Report for period ending 3/31/15 Activities of the CHMA program assistant (1/1/15-3/31/15): During this reporting period, the CHMA assistant provided support to the CHMA program by attending various local CHMA meetings as well as statewide and multi state meetings. Specifically, Mr. Page attended 12 meetings including the following: CHMA grower round table meeting in Sebring (1/7/15), Southeastern Fruit and Vegetable Conference in Savannah (1/8/15 – 1/10/15), Highlands county OJ break (1/22/15), CHMA Hardee county grower forum (1/23/15), Florida citrus show in Ft. Pierce (1/27/15 – 1/29/15), Hardee CHMA meeting (1/30/15), AFVGA (2/5/15 – 2/7/15), IRCHLB meeting (2/9/15 – 2/13/15), CHMA meeting in Ft. Pierce (2/18/15), Highland county grower forum (3/4/15), IRCHLB growers day at CREC (3/12/15), and East coast CHMA organizational meeting (3/19/15). Mr. Page also hosted visitors from Brazil and China who visited to learn more about the CHMA program and exchange information about programs being utilized in other countries. In addition to helping plan and CHMA meetings, Mr. Page continued to keep the CHMA website updated, sending out updates to the individual CHMA listserves, adding names to the listserves, and updating the ACP trend graphs and CHMA rankings. During this period, Mr. Page also worked with USDA ApHIS regarding technical glitches with the scouting data and with Tim Riley’s assistance got this resolved. He also worked with the software company that designed the CHMA mapping program to fix some problems with the program following updates. Mr. Page also continued to work with the new Citrus Economist at CREC to collect data from growers in different CHMAs and use that data to analyze citrus production in trends in areas with and without functioning CHMAs to determine the value of CHMAs in terms of increased production value.
Report for period ending 4/30/14 (FINAL REPORT) During the period of 12/31/14 to 4/30/15 this project focused on completing the season-long field trial examining the potential for movement of neonic residues into nectar to determine whether there was any potential risk of season-long repeated applications of soil-applied neonics to pollinators. These studies were conducted at the request of the EPA in order to maintain the expanded labeling of soil-applied neonics for use in citrus. This field work began in April of 2014 with neonic applications being applied to assigned blocks of 5′ tall trees every 6 weeks. The final plots were treated in October of 2014. Because our previous work suggested that neonics are likely to move into nectar at differing rates, we examined seven different schedules (treatment rotations) of neonics applied every 6 weeks. The rationale for the different rotations was to determine if there was a potential risk identified, could that risk be mitigated by changing the schedule of products applied. During the bloom period in spring of 2015, approximately 200 flowers were collected as pooled samples from ten trees in each plot. There were five replicate plots for each of the 7 rotations examined plus five untreated plots for a total of 40 plots sampled. The blooms from each plot were collected into paper bags and taken back to the lab where the nectar from each bloom was collected using capillary tubes until at least 1 ml of nectar was collected from each plot. The nectar collected was then extracted and frozen for subsequent analysis using LC/MS/MS. Analysis of the nectar showed as expected that there was difference between neonics in likelihood of movement into citrus nectar. However, for all neonics rotations tested, the average expression of residues in nectar was far below the level of concern to pollinators proposed by the EPA. Thus, no significant risk to pollinators was found in this season-long field trial where applications were ceased 2 months prior to bloom (per label directions) for trees 5′ or greater in height. These results confirm our finding in previous studies that under FLorida growing conditions and soil types, repeated use of neonics (every 6 weeks) DOES NOT have a cumulative negative effect in terms of increased neonic expression in nectar.
Report for period ending 6/30/15 (Final Report) Activities of the CHMA program assistant (4/1/15 – 6/30/15): During this reporting period, the CHMA assistant provided support to the CHMA program by attending various local CHMA meetings as well as statewide and multi state meetings. Specifically, Mr. Page attended 11 meetings including the following: Citrus grower’s Institute in Avon Park (4/7/15), citrus extension planning retreat (4/8/15 – 4/9/15), CHMA meeting in Avon Park (4/15/15), Hardee CHMA meeting (4/17/15), CHMA meeting in Immokalee (4/21/15), Volusia county CHMA meeting (4/24/15), CHMA meeting in Wauchula (4/24/15), Lake county grower round table (5/20/15), grower round table discussion in Wauchula (5/21/15), Florida Citrus Mutual Annual meeting (6/17/15), and the East coast CHMA planning meeting (6/24/15). In addition to helping plan and CHMA meetings, Mr. Page continued to keep the CHMA website updated, sending out updates to the individual CHMA listserves, adding names to the listserves, and updating the ACP trend graphs and CHMA rankings. Mr. Page also continued to work with the new Citrus Economist at CREC to collect data from growers in different CHMAs and use that data to analyze citrus production in trends in areas with and without functioning CHMAs to determine the value of CHMAs in terms of increased production value. Over the past year of funding, grower interest and participation in the CHMA program has continued to remain high. At present there are 48 CHMAs functioning across the state with additional groups functioning as CHMAs but not necessarily formalized on the CHMA website. The CHMA program has continued to keep information up-to-date on its website that has been used to document areas where the program is working well and areas where improvement is psyllid control is needed through better coordination of activities. To further document the success and benefits of the CHMA program, information has been gathered from growers from around the state to compare production costs and fruit yields. The results has shown that participation in a CHMA can have a positive effect on fruit yields. Dr. Ariel Singerman presented this information recently at the Florida Citrus Mutual Annual conference in Bonita Springs. These data will help to further increase and motivate grower interest in the CHMA program in the coming year. Plans for the coming funding cycle include further analysis of this type of data to show the continued benefit of participation in a CHMA over time.
Report for period ending 12/31/14 Activities of the CHMA program assistant (9/30/14-12/31/14): During this reporting period, the CHMA assistant provided support to the CHMA program by attending various local CHMA meetings as well as statewide and multi state meetings. Specifically, Mr. Page attended 12 meetings including the following: FFA Meeting (7/2-7/3), American Sociey for Horticultural Sciences meeting (7/25-7/29), Small farms Conference (8/1-8/2), Citrus Expo (8/12-8/14), Gulf CHMA meeting (8/28/14), Grower meeting in Sebring (9/3/14), Hardee CHMA meeting (9/5/14), meeting with county agents (9/12/14), county agent Oj break (9/24/14), Landscape tradeshow (9/25-9/26), FDACS CHMA planning meeting (9/29/14), Hardee county CHMA roundtable (9/30/14). In addition to attending meetings, Mr. Page continued to spend time working with CHMA captains and other interested growers on a daily basis identifying trouble areas, planning programs, and updating website information. Mr. Page also worte an article for Citrus Industry Magazine to update growers on the success of CHMAs statewide and also began working with the new UF/IFAS Citrus Extension Economist to gather data from the CHMA program to conduct an economic analysis of the benefits of CHMA participation.
Report for period ending 12/31/14 Work continued on our previously reported efforts to determine the level of imidacloprid in leaf tissue required to prevent ACP phloem feeding behaviors. This work involved both field studies and concurrent laboratory-based studies. In the field, trees of varying size classes were treated with the recommended rate of imidacloprid. At 2, 4, and 6 weeks post-treatment, leaf samples were collected and analyzed for imidacloprid concentration. The levels of imidacloprid detected in leaf tissue ranged from a low of 2.5 PPM (2,500 PPB) to a high of 12.3 PPM (12,300 PPB), varying with tree size and generally decreasing with increased time following application. However, in some field plots, ACP were observed feeding on treated plants 2-3 weeks following imidacloprid application. Tests of the ACP did not show any decline in susceptibility to imidacloprid where collected from trees with an average level of imidacloprid in leaves of 2-3 PPM (2,000-3,000 PPB). This was in direct contrast to previously published studies suggesting that 200-250 PPB (0.2PPM) is sufficient to control ACP. This finding was examined further in the laboratory by feeding ACP on citrus leaves with a known level of imidacloprid. Our work had previously focused on developing a system for obtaining leaves with a desired level of imidacloprid residues delivered systemically (not foliar application). Using the methods we developed, we fed adult APC on leaves containing 0, 6, 12, 60, 120, and 600 PPM imidacloprid. The results of these feeding studies yielded inconsistent results with as much as 50% survival at the 600 PPM level in some replicates. Based on these results, we suspect that the imidacloprid may be unevenly distributed in the leaf tissue over time, allowing areas of lower concentration for ACP to feed. We are now examining this hypothesis by measuring imidacloprid in different parts of the leaf (center vs leaf margin) to determine movement over time and potentially how long full leaf protection may last.
Report for period ending 9/30/14 During the period of 9/30/14 to 12/31/14 we continued work analyzing leaf tissues in order to more accurately quantify the levels of neonicotinoids present in leaf tissues. Leaf samples from more than 500 trees of different size classes treated with different rates of neonics were ground in liquid nitrogen and any potential pesticide residues within extracted, the extracts then held in the freezer for later analysis. Extracts were then analyzed using LC/MS/MS to quantify the levels of parent compounds and their metabolites in the leaf extracts. While analyses of all samples have not yet been completed, preliminary results show a consistent trend in the quantity of neonic present and tree size/rate of product applied. This work will be continued. Field trials were also continued to build upon work in previous years examining whether soil-applied neonicotinoid applications will move into the citrus flowers during bloom (in particular nectar) and pose any risk to pollinators. These studies are being conducted at the request of the EPA in order to maintain the expanded labeling of soil-applied neonics for use in citrus. Should any potential risks be identified, this project also will identify alternative timing of applications that could be recommended to mitigate any risk that might be identified. This field work began in April of 2014 with neonic applications being applied to assigned blocks of trees every 6 weeks. The purpose was to determine if the neonic applications would accumlate in the plant over time causing excessive risk to pollinators through expression in nectar. Because our previous work suggested that neonics are likely to move into nectar at differing rates, we examined seven different schedules (treatment rotations) of neonics applied every 6 weeks. The final plots were treated in October of 2014. During the next reporting cycle, the plots will be in bloom and we will collect nectar for analysis of potential neonic residues.
July 2015 The objectives of this proposal are 1) to determine if a) leaf litter biodegradation treatments reduce Guignardia spp. pseudothecia and improve control afforded by routine fungicide applications; b) if biodegradation is affected by the current fungicide application practices; and c) whether the biodegradation treatments will affect current citrus best management practices (BMP); 2) to determine the seasonal dynamics of leaf litter inoculum load in varying management regime intensities and how environment affects pseudothecia production in the leaf litter; 3) to test if the resistance to black spot in the leaves and fruit in sour orange is correlated and under simple genetic control through laboratory and field testing of progeny of sour orange crosses in both Florida and Australia. Data was collected for the large field trial and preliminary analysis was begun. The fruit incidence and severity was collected. The manuscript from the experiment to look at the effect of bagasse is still in preparation. Forty leaf litter samples were collected and assayed between January and April 2015 in a Florida grove to obtain a better understanding of the seasonal patterns of spore production in citrus leaf litter. Each sample contained 25 leaves collected from 40 randomly selected trees in a grove near Immokalee in Collier County biweekly. All leaf litter samples were evaluated under the dissecting microscope to assess degradation level. One or more pycnidium and/or pseudothecium from each leaf was examined under the microscope until positive Phyllosticta spp. fructification was identified. Leaves without Phyllosticta spp. fructification were recorded and discarded. Spores were collected by immersing leaf litter in 0.02% Tween 20, and quantification was performed by counting the spores using a haemocytometer. Preliminary weather data were obtained from the Florida Automated Weather Network (FAWN). In Australia, the proportions of the various Phyllosticta fruiting bodies (spermogonia, pycnidia and pseudothecia) were observed by microscopy. The data show a similar pattern to the 2013-14 season, with pycndia dominating at the beginning of the season, then becoming less frequent. Similar peak in pseudothecia production to the 2013-14 season can also be observed, though this peak was smaller and later in 2014-15. In the germplasm inoculation experiments the susceptible controls are starting to show symptoms. The negative controls have not. Sampling will continue for several months. In the parallel microplots for enhanced leaf litter decomposition, it was found that no one treatment over time consistently had the lowest number of fruitifications and all leaves showed similar rates of decomposition. This is similar to what we previously found when examining the rate of decomposition. The amount of water used for fungicides is very high and run-off very common. When the effect of run off was evaluated, there was no improvement for the number of fruiting bodies produced.
July 2015 The objectives of this proposal are 1) to determine if a) leaf litter biodegradation treatments reduce Guignardia spp. pseudothecia and improve control afforded by routine fungicide applications; b) if biodegradation is affected by the current fungicide application practices; and c) whether the biodegradation treatments will affect current citrus best management practices (BMP); 2) to determine the seasonal dynamics of leaf litter inoculum load in varying management regime intensities and how environment affects pseudothecia production in the leaf litter; 3) to test if the resistance to black spot in the leaves and fruit in sour orange is correlated and under simple genetic control through laboratory and field testing of progeny of sour orange crosses in both Florida and Australia. Data was collected for the large field trial and preliminary analysis was begun. The fruit incidence and severity was collected. The manuscript from the experiment to look at the effect of bagasse is still in preparation. Forty leaf litter samples were collected and assayed between January and April 2015 in a Florida grove to obtain a better understanding of the seasonal patterns of spore production in citrus leaf litter. Each sample contained 25 leaves collected from 40 randomly selected trees in a grove near Immokalee in Collier County biweekly. All leaf litter samples were evaluated under the dissecting microscope to assess degradation level. One or more pycnidium and/or pseudothecium from each leaf was examined under the microscope until positive Phyllosticta spp. fructification was identified. Leaves without Phyllosticta spp. fructification were recorded and discarded. Spores were collected by immersing leaf litter in 0.02% Tween 20, and quantification was performed by counting the spores using a haemocytometer. Preliminary weather data were obtained from the Florida Automated Weather Network (FAWN). In Australia, the proportions of the various Phyllosticta fruiting bodies (spermogonia, pycnidia and pseudothecia) were observed by microscopy. The data show a similar pattern to the 2013-14 season, with pycndia dominating at the beginning of the season, then becoming less frequent. Similar peak in pseudothecia production to the 2013-14 season can also be observed, though this peak was smaller and later in 2014-15. In the germplasm inoculation experiments the susceptible controls are starting to show symptoms. The negative controls have not. Sampling will continue for several months. In the parallel microplots for enhanced leaf litter decomposition, it was found that no one treatment over time consistently had the lowest number of fruitifications and all leaves showed similar rates of decomposition. This is similar to what we previously found when examining the rate of decomposition. The amount of water used for fungicides is very high and run-off very common. When the effect of run off was evaluated, there was no improvement for the number of fruiting bodies produced.
The second year’s applications of low concentrations (1/4 rate) of Citrus Fix (2, 4-D) and MaxCel (Cytokinin) with or without ProGibb (GA) every 45 days to Hamlin and Valencia tree canopies at two locations in central Florida for the 2015-16 growing season are underway. Trees were sampled for flowering, early fruit set and spring flush numbers and leaves per shoot. Data is being analyzed and summer shoot development is now being measured. Fruit drop for the 2014-15 season was lower than for the Controls for some treatments. In these replicated plots none of these differences were significant for individual groves except for Hamlins in Haines City, but resulted in only a 2 % reduction from the Control for the 2,4-D plus Maxcel treatment. For pooled data the 2, 4-D plus MaxCel (cytokinin) significantly reduced drop by 6 % and 7 % GA plus 2, 4-D in Hamlins. In Valencia trials the only reduction was for the pooled data for 2, 4-D plus MaxCel, but only a 3 % reduction in fruit drop occurred. A second test of applications GA to roots of nursery trees is ready to start with HLB infected trees. The trees have been infected in a hot psyllid greenhouse. GA stimulated root growth on healthy trees, now we can determine if it can stimulate root growth on infected plants.
Flowering branches were selected for data collection in 4 Hamlin, 4 Valencia, two Murcott and two Sunburst blocks in various locations from Frostproof to Auburndale, FL. Vegetative and flowering buds were tracked for leaf and flower numbers and developmental stages for 2 branch units on each side of the tree row on three trees at each site. All locations have now passed through the various stages of flowering and spring flush development. For Hamlin and Valencia blocks vegetative bud break and leaf feather stage were mostly completed by February 6th, while most flowers were pinhead or popcorn stage. This indicates there is a small window to spray new flush before more effective pesticide sprays need to be stopped. This data will allow us to now make the first restructuring of the Citrus Flower Monitoring System.
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