Test groves were arranged with 5 growers with 11 different tests, 4 of which were sprayed by growers. Seven tests were in Hamlin blocks and 5 are in Valencia blocks. Materials included in tests are Citrus Fix (2, 4-D). Pro-Gibb (GA3), Headline, Gem, Abound and a PGR extract (Ascend) that contains an auxin, GA and cytokinin. Hamlin tests were applied in September or October and Valencia tests in November or December. Data collection includes preharvest fruit drop, total yield and juice analysis on some tests. Hamlin trials are complete and a grapefruit trial has initial results. Some grower applied trial results are as follows: In one trial ProGibb + Citrus Fix reduced drop 8 % over the Control which had 27 % drop. Ascend reduced drop 17 % compared to its Control with 42 % drop. In this trial Headline had no effect. In another trial Headline reduced drop 3.5 % over the Control rate of 26.5 in healthier trees but in declining trees Headline had no effect. In a grapefruit trial initial data found no effect of Headline, but ProGibb, Citrus Fix and the two combined had 11, 13 and 14 % drop, respectively, compared to 20 % drop in the Control. In small plot trials, 2, 4-D reduced drop of healthier and declining trees compared to the Control as did GA and GA + 2, 4-D combined for the declining trees. Neither Headline nor Ascend had an effect on fruit drop in this trial. In an 8 treatment trial near Auburndale, FL no treatment reduced fruit drop compared to the Control. In a trial near Dundee 2, 4-D + GA (18 % drop) and Headline (19 % drop) reduced drop compared to the Control which had 28.5 % drop. In a trial near Frostproof, two formulas of 2, 4-D and ProGibb + Citrus Fix combine reduced fruit drop to 20.5, 17.5 and 14.5 %, respectively, compared to the Control drop rate of 27 %. Data collection for several Valencia trials is now underway. For the Hamlin trials either the traditional GA and/or 2, 4-D or Headline reduced fruit drop about . the time. No factor(s) were obvious as to why they did or did not work in any given instance.
Test groves were arranged with 5 growers with 11 different tests, 4 of which were sprayed by growers. Seven tests were in Hamlin blocks and 5 are in Valencia blocks. Materials included in tests are Citrus Fix (2, 4-D). Pro-Gibb (GA3), Headline, Gem, Abound and a PGR extract (Ascend) that contains an auxin, GA and cytokinin. Hamlin tests were applied in September or October and Valencia tests in November or December. Data collection includes preharvest fruit drop, total yield and juice analysis on some tests. Hamlin trials are complete and a grapefruit trial has initial results. Some grower applied trial results are as follows: In one trial ProGibb + Citrus Fix reduced drop 8 % over the Control which had 27 % drop. Ascend reduced drop 17 % compared to its Control with 42 % drop. In this trial Headline had no effect. In another trial Headline reduced drop 3.5 % over the Control rate of 26.5 in healthier trees but in declining trees Headline had no effect. In a grapefruit trial initial data found no effect of Headline, but ProGibb, Citrus Fix and the two combined had 11, 13 and 14 % drop, respectively, compared to 20 % drop in the Control. In small plot trials, 2, 4-D reduced drop of healthier and declining trees compared to the Control as did GA and GA + 2, 4-D combined for the declining trees. Neither Headline nor Ascend had an effect on fruit drop in this trial. In an 8 treatment trial near Auburndale, FL no treatment reduced fruit drop compared to the Control. In a trial near Dundee 2, 4-D + GA (18 % drop) and Headline (19 % drop) reduced drop compared to the Control which had 28.5 % drop. In a trial near Frostproof, two formulas of 2, 4-D and ProGibb + Citrus Fix combine reduced fruit drop to 20.5, 17.5 and 14.5 %, respectively, compared to the Control drop rate of 27 %. Data collection for several Valencia trials is now underway. For the Hamlin trials either the traditional GA and/or 2, 4-D or Headline reduced fruit drop about . the time. No factor(s) were obvious as to why they did or did not work in any given instance.
Test groves were arranged with 5 growers with 11 different tests, 4 of which were sprayed by growers. Seven tests were in Hamlin blocks and 5 are in Valencia blocks. Materials included in tests are Citrus Fix (2, 4-D). Pro-Gibb (GA3), Headline, Gem, Abound and a PGR extract (Ascend) that contains an auxin, GA and cytokinin. Hamlin tests were applied in September or October and Valencia tests in November or December. Data collection includes preharvest fruit drop, total yield and juice analysis on some tests. Hamlin trials are complete and a grapefruit trial has initial results. Some grower applied trial results are as follows: In one trial ProGibb + Citrus Fix reduced drop 8 % over the Control which had 27 % drop. Ascend reduced drop 17 % compared to its Control with 42 % drop. In this trial Headline had no effect. In another trial Headline reduced drop 3.5 % over the Control rate of 26.5 in healthier trees but in declining trees Headline had no effect. In a grapefruit trial initial data found no effect of Headline, but ProGibb, Citrus Fix and the two combined had 11, 13 and 14 % drop, respectively, compared to 20 % drop in the Control. In small plot trials, 2, 4-D reduced drop of healthier and declining trees compared to the Control as did GA and GA + 2, 4-D combined for the declining trees. Neither Headline nor Ascend had an effect on fruit drop in this trial. In an 8 treatment trial near Auburndale, FL no treatment reduced fruit drop compared to the Control. In a trial near Dundee 2, 4-D + GA (18 % drop) and Headline (19 % drop) reduced drop compared to the Control which had 28.5 % drop. In a trial near Frostproof, two formulas of 2, 4-D and ProGibb + Citrus Fix combine reduced fruit drop to 20.5, 17.5 and 14.5 %, respectively, compared to the Control drop rate of 27 %. Data collection for several Valencia trials is now underway. For the Hamlin trials either the traditional GA and/or 2, 4-D or Headline reduced fruit drop about . the time. No factor(s) were obvious as to why they did or did not work in any given instance.
Three growers are appling1/4th the regular rate of Citrus Fix and MaxCel every 45 days on approximately 1 acre each of Hamlin and Valencia orange trees. Grove locations are Sebring, Babson Park and Ft. Meade. The last applications for this growing season are scheduled for October. Growers have been diligent in making timely applications. Fruit drop will be measured and yields obtained for Hamlin blocks. If further support is provided for this project, Valencia yields and drop as well as flowering will be checked for any difference in timing or intensity and applications will be made for a second year.
No additional treatments or data collection occurred during this period. Data will be summarized in the final report.
There were no additional tests or measurements during this period. Results will be summarized in the Final Report for the project.
Test groves were arranged with 5 growers with 11 different tests 4 of which will be sprayed by growers. Seven tests are in Hamlin blocks and 5 are in Valencia blocks. Materials included in tests are Citrus Fix (2, 4-D). Pro-Gibb (GA3), Headline, Gem, Abound and a PGR extract that contains an auxin, GA and cytokinin. Hamlin tests were applied in September or October and Valencia tests in November or December. Data collection will include preharvest fruit drop, total yield and juice analysis on some tests particularly if Headline is included.
Low concentrations (1/4 rate) of 2, 4-D and Max-Cel were applied every 45 days to Hamlin and Valencia tree canopies at two locations in central Florida starting in Spring 2014. Concentrations were 12.6 ml Citrus Fix and 480 ml Max-Cel. Every other 45 day period, GA3 (0.04 g ai/tree) was applied in 3 gal of water per each microjet irrigation zone. Treatments were applied from Spring through October. Trees were sampled in late spring for phloem development at four locations in the scaffold system (root flare, trunk, small scoffolds and leaf main veins). Comparable samples will be taken at the end of the growing season to compare phloem development with and without the PGR treatment. Comprehensive PGR profiles on the treatments were run by Dr. Killiny. Almost all of the treatment trees were positive for HLB. Fruit drop and fruit per tree data are now being collected. Root densities and canopy condition will also be evaluated.
The person to redo the Internet model for flowering evaluation was identified and hired to start work in December. Data collection and rewriting code will be done from December through January. Off season blooms related to HLB stresses are a problem that needs to be dealt with. We will try to program them if their induction relates to mild or moderate water stress periods.
This project, in general, seeks to determine if there are any observable influences of foliar fertilizers on HLB-affected grapefruit in the Indian River marketing district. To-date, this project has established 3 separate research trials in commercial grapefruit groves and university research farms in St. Lucie county, Florida. Trial #1 is ~25 years old of ‘Flame’ grapefruit on Swingle rootstock. Trial #2 utilizes ~6 year old ‘Ruby Red’ on Sour orange trees. The first 2 trials are located in commercial groves. Trial #3 seeks to determine the effect(s) that foliar fertilizers have on young tree growth and their ability to protract HLB disease symptoms in 1 year old ‘Ray Ruby’ grapefruit on Kuharske rootstock. For trial #1, there are a total of 30 replicated experimental units; for trial #2, there are a total of 50 replicated experimental units; and, for the trial #3, there are a total of 24 replicated experimental units. Foliar fertilizer applications have been started since February 2014. Tree growth data, leaf nutrition data, and CLas titer measurements have been made. Fruit drop monitoring will begin in September 2014 in trials #1 and #2. In prosecution of these efforts, 2-part-time OPS employees have been hired to do our foliar sprays and collect data observations. We also completed the refurbishment of a mobile fruit grading line. Fruit quality and quantity assessments will begin in late fall/early winter of 2014.
The insectary at the Florida Department of Agriculture and Consumer Services, Division of Plant Industry (DPI) was a longstanding source of Diaprepes root weevil larvae for researchers in Florida and elsewhere. Reduced demand for these larvae caused this agency to discontinue their production in September 2014. In anticipation we met several times with the agency to learn their methodology. We purchased cages and supplies and constructed an insectary, acquired adult weevils and began rearing larvae on diet in axenic conditions. To date we have produced 4 ‘production runs’. Contamination of cultures in which the larvae grow has been a problem, but fewer units have become contaminated over time. We will have enough 3-5 instar larvae going into the winter season to conduct the upcoming field trials at sites in Lake and Polk Counties. Repeated experiment using H. floridensis, validating results reported in previous report. We shall include H. floridensis in upcoming field trials.
Entomopathogenic nematodes: Amending soils to increase biological control of insect pests We repeated experiments to test whether EPN community structure can be engineered by managing soil water potential (see June 2014 report for results). Mixtures of Sd, Sx, Hi, and Hz were maintained with weevil larvae in soil low and high water potential. EPNs that recycle in weevils were periodically added to fresh columns with weevil larvae for several ‘generations’ (21 days each). During the first three ‘generations,’ Sd gradually, but consistently increased its presence in the EPN population from 45% to 55% in the dry (6% moisture) soil and remained steady at 22-30% in the wetter (18% moisture) soil. Steinernema sp. (Sx) constituted between 27-41% of EPNs in dry soil and 55-63% in moist soil, whereas Hz represented between 6-23% of EPNs without an effect of soil moisture. It is interesting that Hi did not persist in any treatment, given that Hi is the dominant EPN species in all of the ecoregions where citrus is grown. We reported that Hi is little affected by Catenaria spp., a fungal predator of nematodes, whereas the fungus is lethal to most other EPN species in controlled studies. Similarly, during monthly sampling for two years in 4 citrus groves, detection of Catenaria sp. was found to be inversely related to Sd abundance and positively related to Hi abundance (unpublished). Results such as these suggest the need to increase the complexity of the biota in these experiments to include natural enemies of EPNs in order to recreate selection pressures in microcosms that produce EPN communities comparable to those in the field. A future microcosm experiment will test this hypothesis. We continued comparing the biology of two closely related native species, Steinernema diaprepesi (Sd) and Steinernema sp. (Sx), with respect to survival mechanisms. When subjected to a range of relative humidity (50%-100%), Sx did not survive RH ‘90% whereas, Sd persisted on filter paper disks at 90% and greater RH. Moreover, when the two species were maintained 48 h in aqueous solutions of 30% glycerol, both lost volume with the loss of water but, upon rehydration for 24 h, most Sd became motile whereas all Sx ruptured. Thus, Sd (an inhabitant of well drained, central ridge soils) has superior capacity for osmoregulation and desiccation survival compared to Sx (an inhabitant of poorly drained, flawoods soils). An inferior capacity for osmoregulation may also affect the spatial pattern of Sx which has not been detected in coastal orchards where hypertonic conditions tend to be greater than in the inland flatwoods orchards. Plant parasitic Nematodes: Characterizing a new nematode pest and the prevalence of resistance breaking populations of the citrus nematode. Treated plots two nematicide trials conducted in east coast grapefruit on swingle. We identified a second site on the central ridge with 18-month-old trees heavily infested by dagger nematode (Xiphinema vulgare). Installed irrigation lines adjacent to exiting lines to initiate nematicide trials (oxamyl and an experimental nematicide/fungicide) that will continue for three years.
The project began on May first 2014 with two citrus groves selected for the project. A mature grove owned by English Bothers consists of 20 year-old Hamlin sweet orange trees predominately on Swingle rootstock. Sixteen full row main plots of 40 trees each were selected for irrigation water acidification at one of four target water pH (7.5, 6.0, 5.0, and 4.0). The second experimental site was established in a block of two year old Hamlin sweet orange trees on Swingle rootstock at Orange-Co’s Joshua block. Rows of trees with similar treatment plots were selected randomly with one row split into two main plots of 20 trees each. Initial soil measurements, indicated that soils at both sites were alkaline with average soil pH of 7.43 for English Bothers and 7.05 for Orange-Co. After irrigation water acidification treatments were initiated, soil pH at both sites decreased by October, 2014 to a range of 6.24 to 6.55 with no significant differences for treatment at either site. Soil ph in control blocks with no acidification remained at 7.3 for English Brothers and declined to 6.55 at Orange-Co. These treatments were applied during the rainy season with little irrigation applied at both sites. A total of approximately 39 minutes of irrigation at was recorded for a four month period (July through September) at Orange-Co. Irrigation during these four months were primarily to apply acidifying fertigation. Likewise, no significant differences in tree trunk measurements (17.0to 21.1 Mm), Phytophthora propagules (0.008 to 0.02 propagules/mg soil) ir root density (0.07 to 0.31 mm root/mm soil at 0-15 cm and 0.01 to 0.03 mm/mm at 15 to 30 cm) were found in June, indicating no difference in tree size due or root pathogen density for the acidification treatments. These results indicate that little soil acidification occurred during the summer rainy season because of low irrigation inputs.
Feb 2014 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: All preliminary experiments have been completed for propiconazole, difenoconazole, and tetraconazole. Preliminary experiments with imazalil and fenbuconazole are on-going Objective 2: We’ve taken our first rating in the fungicide trial and will continue until fruit harvest. Too early to say how treatments are going to shake out. We are planning for next season’s trial. CBS lesions are now apparent on fruit at most sites so we’re planning to start some of the survey data next week. Objective 3: Suitable sites to conduct the spatial studies have been located. This study will begin in earnest close to fruit maturity when symptoms become apparent. Objective 4: Since the last progress report, work has continued evaluating the efficacy in vitro of the postharvest citrus fungicides imazalil (Freshgard 700, Active Ingredient: 44.6%) and pyrimethanil (Penbotec 400, Active Ingredient: 37.14%) at concentrations of 0.001, 0.01, 0.1, 1, and 10 mg/l active ingredient in the PDA medium on mycelial growth inhibition of four Guignardia citricarpa isolates. After 14 day, there was a near log-linear increase in mycelial growth inhibition increasing with 100% inhibition at the highest concentration. To evaluate heat effects on G. citricarpa, balls of mycelial masses cultured in liquid media were placed in solution at 55C for 0.5, 1, 2, 3, 4, 5, or 6 minutes, the flasks cooled by placing in an ice-water bath, the mycelia plated on . strength PDA media, and growth measured over 10 days. The control was exposed only to a solution at 25C. No treatment duration killed the G. citricarpa, but 55C exposure for 1 min reduce mycelial growth by half, and inhibition gradually increasing to about 75% after 6 minutes exposure. Neither chitosan at low concentrations (0.5 ‘ 10 mg/L), nor 50, 100, 200, or 300 mg/L salicylic acid (SA) inhibited G. citricarpa mycelia growth, but instead appeared to stimulate its growth slightly (SA) to moderately (chitosan) in the mid to higher concentrations tested. These experiments will be repeated.
We have compared the qualitative and quantitative expression in plants of amiRNAs engineered to target psyllids by directly expressing them from Agrobacterium tumefaciens, by using Tobacco mosaic virus (TMV) and by using a modified Begomovirus expression system (Tomato mottle virus, A component, TAV). Based on the results of Hi-seq illumina deep sequencing, TAV is the best candidate to express artificial microRNAs in plants. We are currently evaluating more samples by deep sequencing and engineering additional constructs to target psyllids. Objective 2 is to evaluate and optimize in planta expression of anti-psyllid interfering RNAs. We have started the leaf-disc feeding assays using our transgenic plants expressing double-stranded RNAs expressed from two different promoters (the 35S promoter for general tissue expression and the AtSuc2 promoter for phloem-specific expression) and the in planta transient expression of specific artificial microRNAs. So far the transient delivery/expression system has not worked for citrus. Thus, we are evaluating additional candidate interfering RNAs by in vitro feeding assays, and evaluating specific interfering RNAs in citrus plants infected with recombinant Citrus tristeza virus (CTV). The latter is in collaboration with Dr. W. O. Dawson. We have also been optimizing the conditions of our on plant feeding tests to have them close to natural feeding environment.
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