Entomopathogenic nematodes: Amending soils to increase biological control of insect pests We sampled the Bartow experiment in which soil pH was reduced with elemental sulfur. Soil pH was significantly reduced in December 2012, but the treatment had no effect on population density of Paenibacillus sp. or Steinernema diaprepesi (December report). By February-March the bacterial populations in control plots (high pH) were nearly 18-fold greater (P=0.02) than in sulfur treated plots. The S. diaprepesi populations were more than twice as large in sulfur treated plots as in untreated ones (P=0.04). Therefore, we have increased an indigenous entomopathogenic nematode population by modifying the soil chemistry, and a corresponding reduction in levels of a natural enemy of the nematode suggests a mechanism for the response we observed. We observed an additional potential benefit of reducing soil pH at this site, because citrus nematode numbers from December through March were 4-fold greater (P=0.02) in control plots than in plots treated with sulfur. However, there was a slight non-significant trend toward fewer fibrous roots on sulfur treated trees that requires further study. We will continue to evaluate the effect of this treatment quarterly throughout 2013. We are also evaluating the effects of soils from the two treatments at Bartow on the EPNs S. diaprepesi and H. indica independently of the bacterium in controlled studies in the laboratory. The manuscript ‘New citriculture system suppresses native and augmented entomopathogenic nematodes’ Campos-Herrera, R., Pathak, E., El-Borai, F., Schumann, A., Abd-Elgawad, M.M., Duncan, L.W. was accepted for publication in Biological Control. Plant parasitic Nematodes: Characterizing a new nematode pest and the prevalence of resistance breaking populations of the citrus nematode. We Initiated a nematicide trial to evaluate the tree response to dagger nematode control in an 8 acre block of 3-year-old Flame grapefruit on Cleopatra mandarin rootstock. Valves were installed variously at north and south ends of 8, double-row beds in order to created 12 untreated plots of 8 trees each, paired with 12 Vydate-treated plots of 8 trees each. Valves were also installed on additional beds to prevent Vydate treatment of trees. Some of these beds were plumbed to receive a dose response trial of an experimental DuPont compound that has shown excellent efficacy against sting nematode, Belonolaimus longicaudatus. The DuPont compound has an added benefit of a much lower mammalian toxicity than does Vydate. Other beds were plumbed to receive treatments to evaluate 2 experimental nematicides being developed by Bayer. The site had very regular and abundant levels of dagger nematodes across all beds and HLB is evident throughout the block. The 3 trials initiated here should provide important information about the effects of these nematodes on HLB affected trees and also generate data concerning the efficacy of urgently needed additional nematicides for use in Florida.
This research seeks to determine whether young trees infected with CLas and displaying typical HLB symptoms can be brought to maturity and produce an economically viable yield. This will be achieved by managing a 60 acre grove of 3-year-old ‘Valencia’ / Kuharske Carrizo trees using a combination of three different foliar and three different ground applied nutritional programs. The trial block is located in Ben Hill Griffin (BHG) commercial groves near Venus, Florida and was planted in December 2008 at a density of 151 trees/acre with tree rows oriented north-south. The grove has been scouted for HLB four times in November 2009, November 2010, April 2011 and August 2011, and 8, 11, 3 and 1258 infected trees were found in each scouting cycle, respectively. These finds represent infection rates of 0.09%, 0.12%, 0.03% and 13.89%, for a cumulative infection level of 14.13%. Psyllid control has been provided with soil drench applications of the systemic neonicotinoid insecticide imidacloprid up to the maximum per acre annual limit. Supplemental foliar applications of insecticides have been made using pyrethoid and organophosphate pesticides. The treatments were initiated in March 2012, before the grant funding cycle began, in order to capture the full growing season. By July 2012 when the project was officially started, the HLB incidence in the block was so widespread that it was impossible to separately identify and sample uninfected trees, so that the separate measurement of “HLB” versus “healthy” for comparison was dropped. Factorial AxB treatments consist of A) ground-applied: 1) Liquid/dry+Ca (BHG standard), 2) Liquid+Ca, 3) Liquid/dry-Ca B) foliar-applied: 1) BHG standard-Ca, 2) BHG standard+Ca, 3) “Prescription”(+Ca). The prescription treatment was designed to be dynamic, customized for optimization, with feedback based on frequent leaf tissue analyses, visual symptoms, and the growth of the tree canopies and yield. There are six replications of treatments, with two being pure replications. Leaf tissue analysis conducted in June 2012 indicated that N was high in all treatments, P and K were optimum, Mg was marginally low, Ca was low in all treatments, and S, Zn, Mn, Fe were all optimum. B was marginally low in all treatments, and Cu was optimum to marginally high in all treatments. We will monitor the tree growth in each plot to compare canopy growth rates, fruit yield and quality. These data will be correlated with leaf and soil analyses in an effort to determine the factors contributing to tree growth and yield in the presence of HLB.
We proposed to identify and assess gene sequences for their negative effects on sap-sucking Hemipteran insects via RNAi using both in vitro and in planta dsRNA feeding assays. To date, we have cloned sequences from nine homologous D. citri and M. persicae transcripts. In addition, we have carried out artificial feeding assays on M. persicae using dsRNA derived from the salivary gland-specific Coo2, midgut-specific glutathione-S-transferase S1 (GSTS1) and constitutively expressed S4e ribosomal protein from M. persicae, as well as a control derived from green fluorescent protein (GFP) sequence. Since recent evidence suggests that RNAi in sap-sucking insects may operate more effectively in planta than in vitro, we evaluated the RNAi strategy in planta for its effects against our model insect, M. persicae (objective 2). In this objective, Gateway-based vectors were used to express the selected insect dsRNA (Coo2, GSTS1 and S4e) either constitutively (35S promoter) or in a phloem-specific manner. Our results suggest that the M. persicae-specific dsRNA expressed in planta has a negative effect on both the lifespan of the insects and the number of offspring generated. In the fall of 2010, we began working on objective 3: to transform citrus with RNAi-inducing transgenes against D. citri. Previously, we conducted 3′ rapid amplification of cDNA from vacuolar ATP synthase subunit G, S4e, and .-tubulin transcripts from D. citri. We have now inserted sequences of the aforementioned transcripts into Gateway-based vectors downstream of both the constitutive 35S and our novel phloem-specific citrus CsSUS1 promoters. To date, we have completed three rounds of transformation and regeneration of citrus lines with the D. citri-specific gateway vectors for greenhouse evaluation. This first round generated several lines containing gateway vectors with the vacuolar ATP synthase subunit G or S4e transcripts inserted downstream of a phloem-specific citrus CsSUS1 promoter. We have now regenerated at 2-3 lines for each of the constructs of interest. In order to boost the number of regenerant shoots for micropropagation we developed an alternative transformation/regeneration process for citrus that would generate numerous shoots (10-20) per transformant. The process appears to be working with Citrus plants containing most of the constructs developed to date. We have formalized an evaluation pipeline with collaborators in Florida for regenerant evaluation and attempting to develop larger numbers of lines.
We proposed to identify and assess gene sequences for their negative effects on sap-sucking Hemipteran insects via RNAi using both in vitro and in planta dsRNA feeding assays. To date, we have cloned sequences from nine homologous D. citri and M. persicae transcripts. In addition, we have carried out artificial feeding assays on M. persicae using dsRNA derived from the salivary gland-specific Coo2, midgut-specific glutathione-S-transferase S1 (GSTS1) and constitutively expressed S4e ribosomal protein from M. persicae, as well as a control derived from green fluorescent protein (GFP) sequence. Since recent evidence suggests that RNAi in sap-sucking insects may operate more effectively in planta than in vitro, we evaluated the RNAi strategy in planta for its effects against our model insect, M. persicae (objective 2). In this objective, Gateway-based vectors were used to express the selected insect dsRNA (Coo2, GSTS1 and S4e) either constitutively (35S promoter) or in a phloem-specific manner. Our results suggest that the M. persicae-specific dsRNA expressed in planta has a negative effect on both the lifespan of the insects and the number of offspring generated. In the fall of 2010, we began work toward the transformation of citrus (objective 3) with RNAi-inducing transgenes against D. citri. Previously, we conducted 3′ rapid amplification of cDNA from vacuolar ATP synthase subunit G, S4e, and .-tubulin transcripts from D. citri. We have now inserted sequences of the aforementioned transcripts into Gateway-based vectors downstream of both the constitutive 35S and our novel phloem-specific citrus CsSUS1 promoters. To date, we have completed three rounds of transformation and regeneration of citrus lines with the D. citri-specific gateway vectors using all of the aforementioned constructs in combination with various promoters. We generated several lines containing gateway vectors with the vacuolar ATP synthase subunit G, S4e, and .-tubulin transcripts inserted downstream of a phloem-specific citrus CsSUS1 promoter and under constitutive control. Overall, we regenerated at 2-3 lines for each of the gene and promoter combination of interest. Given that the traditional transformation/regeneration process produced few plants for evaluation, we attempted to implement an alternative transformation/regeneration process for citrus that would generate numerous shoots (10-20) per transformant. This would serve as material for in vitro micro propagation to produce many copies of each line for evaluation. This process appears to be working with transgenic Citrus plants from the second and third rounds of transformants/regenerants. We are in process of reaching out to an evaluation pipeline with collaborators in Florida. In summary, we have identified RNAi candidates that appear to negatively impact the lifespan and reproduction of phloem-feeding insects. We have cloned analogues of the candidates from D. citri and have we completed three rounds of transformation and regeneration of citrus lines with the D. citri-specific gateway vectors using several promoters including citrus CsSUS1p. In the absence of an evaluation pipeline for D. citri in NY, we used developed lines to optimize an alternative transformation/regeneration process for citrus that would generate numerous shoots (10-20) per transformant. We are in discussion with collaborators in Florida in regards to participating in an evaluation pipeline.
Soil and leaf samples have been collected in spring (dry) and summer (rainy) seasons for the past two years. Imidacloprid rates have been applied at 1X, 2X and 4X lable rates on transplants (1-2 yrs), moderate age (5-7 yrs), and mature trees (>10 yrs) each season. Bromide has been applied with each application to serve as a tracer for the wetting front. Psylid populations were surveyed weekly following applications. soil and leaf extracts have been analyized using IMD. Water movement has been monitored using soil capacitance sensors with all measurements ranging between field capacity and 40 percent depletion for all irrigation rates. Bromide concentrations fell to zero at all applications by 8 days after application Soil Imidicloprid concentrations for the 1X rate start at less than 2.5 .g per mg soil in the upper 15 cm of soil. Within five days after application, imidaploprid concentrations in the 0-15 cm depth are reduced to less than 0.5 .g per mg soil by tree uptake or movement to deeper depths. Soil Imidacloprid concentrations at 15- 30 an 30-45 cm remain below 0.5 .g per mg soil for the duration of the study. The 2X and 4X applications typically have proportionally greater soil concentrations in the 0-15 cm depth and decrease to less than 1 .g per mg soil. Deeper soil depths typically never increase above 0.5 .g per mg soil. These results would indicate that Imidacloprid moves with the wetting front with low soil residual concentrations. Pysillid populations fell to near zero for approximately 15 days after application for all application rates for all tree ages. The Pysillid populations of the 1X application rate increased to pre-treatment counts within 21 days of application. Pysllid populations in the 2X and 4X applicaitons remained below 0.5 Pysillids per tree to 70 days after application for the transplanted trees, and increased to more than 1 pysllid per tree by 35 days after application for the moderate age trees and 57 days for the mature trees. These data would indicate that higher application rates will be required for trees more than 5 yrs of age. .
We proposed to identify and assess gene sequences for their negative effects on sap-sucking Hemipteran insects via RNAi using both in vitro and in planta dsRNA feeding assays. To date, we have cloned sequences from nine homologous D. citri and M. persicae transcripts. In addition, we have carried out artificial feeding assays on M. persicae using dsRNA derived from the salivary gland-specific Coo2, midgut-specific glutathione-S-transferase S1 (GSTS1) and constitutively expressed S4e ribosomal protein from M. persicae, as well as a control derived from green fluorescent protein (GFP) sequence. Since recent evidence suggests that RNAi in sap-sucking insects may operate more effectively in planta than in vitro, we evaluated the RNAi strategy in planta for its effects against our model insect, M. persicae (objective 2). In this objective, Gateway-based vectors were used to express the selected insect dsRNA (Coo2, GSTS1 and S4e) either constitutively (35S promoter) or in a phloem-specific manner. Our results suggest that the M. persicae-specific dsRNA expressed in planta has a negative effect on both the lifespan of the insects and the number of offspring generated. In the fall of 2010, we began working on objective 3: to transform citrus with RNAi-inducing transgenes against D. citri. Previously, we conducted 3′ rapid amplification of cDNA from vacuolar ATP synthase subunit G, S4e, and .-tubulin transcripts from D. citri. We have now inserted sequences of the aforementioned transcripts into Gateway-based vectors downstream of both the constitutive 35S and our novel phloem-specific citrus CsSUS1 promoters. To date, we have completed two rounds of transformation and regeneration of citrus lines with the D. citri-specific gateway vectors for greenhouse evaluation. This first round generated several lines containing gateway vectors with the vacuolar ATP synthase subunit G or S4e transcripts inserted downstream of a phloem-specific citrus CsSUS1 promoter. We have now regenerated at 2-3 lines for each of the constructs of interest, but have to terms with the fact that the transformation process produces few plants for evaluation. In response, we attempted to develop an alternative transformation/regeneration process for citrus that would generate numerous shoots (10-20) per transformant. This would serve as material for in vitro micro propagation to produce many copies of each line for evaluation. Thus far this process appears to be working with transgenic Citrus plants from the second round of transformants/regenerants. We are formalizing an evaluation pipeline with collaborators in Florida, and have completed a third round of transformations and are regenerating additional lines with other transcript/promoter combinations such as a B tubulin subunit from D. citri.
The Unforbidden Fruits project goal is to undercut the demand for smuggled budwood and product by making available disease-tested propagating material for citrus and citrus relatives in demand by ethnic and religious communities in California. Smuggled citrus and citrus relatives present the danger of introducing pests and diseases of quarantine significance. Two major focuses of the project are curry leaf (Bergera koenigii) and bael (Aegle marmelos). We have distributed several hundred seeds of curry leaf and bael to four interested citrus nurseries. Growers are concerned about planting curry leaf or bael next to commercial citrus because it is a prime host of the Asian citrus psyllid (ACP), the vector of Huanglongbing (HLB) disease (Candidatus Liberibacter spp.). Recent ACP discoveries in the San Joaquin Valley have made growers reluctant to plant these citrus relatives. The quickest and most efficient way to propagate curry leaf and bael would be by tissue culture. One nursery has expressed interest in this, but has not yet started the process. The ideal situation for growing curry leaf and bael in California would an insect-protected greenhouse in a non-citrus growing area. Curry and bael trees would grow faster in a climate-controlled environment and with the proper regulatory updates could be shippable, like certified nursery stock, even from an ACP or HLB quarantine zone. The major obstacle is cost. We continue to guide aspiring growers of citron (Citrus medica) ‘ both Orthodox Jews on the East Coast and hands-on farmers in California ‘ to fulfill the applicable phytosanitary and religious laws in starting up citron plantings. In the past three years at least four new plantings have gone into the ground or been planned in California, in Coachella, Valley Center, Orange Cove, and Fresno; there is also one in Yuma, Arizona. All these plantings so far have been established by seed propagation. Trees of ‘Assads’ citron (a never-grafted line brought from Morocco) in the UCR Citrus Variety Collection will fulfill the three-year Orlah requirement on July 1, 2013, at which time trees planted from its seeds will be fully kosher for Jewish ritual use. ‘Morning Song Temoni’, another never-grafted line, will fulfill Orlah in 2015. Seeds from these trees may not meet the standards of the most exigent buyers and commercial growers, but will provide a supply for moderately religious Jews who want ungrafted trees. Woodapple (Limonia acidissima) is a citrus relative whose fruits are much sought and sometimes smuggled into California. It rarely fruits in Riverside, but a tree at the UCR Citrus Variety Collection is bearing fruits this year that will provide seeds for further propagation. Pummelo (Citrus maxima) is perhaps the most important of Citrus species from the epidemiological standpoint. We have requested exotic pummelo germplasm from local sources on multiple occasions, so far without success; we will continue to pursue this objective.
Dec 31 2012 The objective of this project is to investigate three questions: 1) whether HLB symptoms or boron/zinc deficiencies alone affect how ACP responds to citrus; 2) whether feeding patterns by adults, length and location of feeding, are altered by HLB infection or boron/zinc deficiencies; and 3) whether different strains of Ca. Liberibacter asiaticus (Las) differentially affect the response of ACP to citrus. In other pathogen/host/vectors systems, such as that with Ca. Phytoplasma mali and Cacopsylla picta (the apple psyllid), the pathogen manipulates the plant host metabolism so that diseased plants become more attractive to the psyllid vector, thereby spreading the pathogen more rapidly than if no plant host manipulation occurred. Since nutrient deficiencies are often associated with HLB in citrus, we wished to confirm that the reported attraction of Diaphorina citri to HLB symptomatic plants over uninfected plants was due to changes in host metabolism by the pathogen rather than physiological changes due to poor nutrition. Trees have been cut back to produce new flush for up-coming experiments with psyllids. Samples have been sent for nutrient analysis to determine the nutrient levels at the time of experimentation.The OPS that is working on the project has been following members of the Stelinsky lab to learn how to handle and work with the insects in the olfactometer. We have also build additional apparati for the visual cues experiment and the settling experiments.
March 30, 2013 The objective of this project was to investigate three questions: 1) what is the seasonal pattern of Ca. Liberibacter asiaticus (Las) prevalence in leaf tissue on a grove scale; 2) what are the flushing patterns of citrus and do the flushing patterns affect the prevalence of Las in Diaphorina citri or citrus leaves; and 3) what is the prevalence of Diaphorina citri carrying Las on a grove scale and how does it compare the results from the citrus trees in the same grove. In 2008 and 2009 Ebert and Rogers demonstrated that the prevalence of Las in the Asian citrus psyllid (ACP) varied seasonally but the pattern between seasons was not consistent. It was suggested that perhaps the reason for the differences between the years related to the flushing patterns of citrus and the prevalence of the bacterium in the leaves where ACPs are feeding. This project aims to determine if there is a relationship between the frequency of disease on branches and ACPs. Sample collection of psyllids, phenology and plants is continuing this spring. Psyllids continue to be difficult to collect but we attempt to collect every 2 weeks. This is a positive result for the industry but has made this project more complicated. Plant and psyllid samples have begun to be extracted again. PCR will begin shortly to be calculate the pool size for the remaining samples. This will help to clear the back log of samples and get the project back on track.
The objective of this project was to investigate three questions: 1) How long does a leaf needs to be infected by Guignardia citricarpa before ascospore production can be initiated; 2) How does infection and colonization of leaves by Guignardia citricarpa occur and potentially showing how pseudothecia, the sexual spore producing structures, are produced; and 3) what is the interaction between the common twig colonizing pathogen Diaporthe citri and the black spot pathogen Guignardia citricarpa and whether they can co-exist to successfully sporulate on dead twigs. The second end of the mating him has been found through sequence analysis. DNA was isolated from 47 isolates of G. citricarpa and found that they contain the same mating gene. Anothere 36 isolates will be tested to see if another gene is found. We are studying the implications of these findings. We continue to look for the flanking regions of the MAT locus to confirm that we have the whole gene. Further testing of the GFP labelled strain. We have found that germinated conidia appear not to contain GFP nor the selectable marker hygromycin. Further DNA extraction and PCR will be conducted to confirm this. We are also attempting to transform with Agrobacterium but so far no positive results. The DNA of G. mangiferae has been clean up for sequencing. Once the DNA quality is verified, it will be sent out for genome sequencing using Ion Torrent.
This project was originally conceived in response to a request from the Florida Citrus Production Research Advisory Council (FCPRAC) for a proposal to support a citrus extension entomologist in SW Florida with a companion project on the East Coast. Both proposals were approved and initiated in 2008. A year later, FCPRAC became CRDF and we wrote a new proposal reflecting the Foundations’s research focus which included 5 objectives: (1) evaluate efficiency of control techniques for Asian citrus psyllid (ACP) in cooperation with growers, (2) develop efficient monitoring methods for ACP, (3) accelerate testing of new chemistries and techniques for ACP management, (4) evaluate the economic component of the comprehensive program, and (5) provide an information bridge between researchers, growers, and industry. The project was approved for 3 years but was terminated 30Apr2012 by the executive CEO for the stated reason that different objectives were being pursued. This was in fact the case, as the original objectives had either been accomplished and/or passed on to other projects. The following is a final report summarizing some of the accomplishments of this project. Objective 1: The “dormant spray” grew out of observations of the difficulty controlling ACP when flush is present, rapid development of populations in spring flush and the need to prevent subsequent dispersal and spread of HLB. The hypotheses was that overwintering populations of adult ACP would be vulnerable to broad-spectrum insecticides whereas many beneficial insects absent at that time would not. Proof of concept was obtained from two large scale trials conducted in a commercial grove and results disseminated through talks, trade journal articles and peer reviewed publications cited on our website www.imok.ufl.edu/entomology. Aerial and low volume ground applications of insecticides and horticultural mineral oil were also investigated. Area wide cooperative dormant sprays were initiated over the 120,000 citrus acres in the Gulf Region in 2008 and became the basis of the widely lauded Citrus Health Management Area (CHMA) program which now includes 38 “CHMAs” throughout the state. Objective 2. The stem tap sample was first developed and tested for a cooperative study of psyllid populations throughout the state and later published in the Journal of Economic Entomology. A randomly chosen branch is struck 3 times with a stick or length of PVC and adult ACP falling on a laminated sheet are counted. Instructions were posted on our website and many hundreds of scouts were trained. Rapid, reproducible and usable under most conditions, the tap sample has become a standard scientists, growers and consultants and was adopted by the Citrus Health Management Program of USDA-APHIS and FDACS-DPI for their ongoing campaign to monitor 6,000 citrus blocks throughout the state. Objective 3. Over 30 replicated trials testing more than 40 labeled and experimental active ingredients in close to 300 treatments were conducted at SWFREC or in commercial groves. Reports are available on our website, and were published in the Entomological Society of America’s “Arthropod Management Tests” and the Proceedings of the Florida State Horticultural Society. Results were also summarized through talks, trade journal articles, EDIS publications and recommendations made to growers. Objective 4: Economic analyses of insecticide programs and yield responses have been reported through CRDF projects 179 and 331. Objective 5. Presentations and publications can be found on our website. Adoption in Florida and beyond of tactics, strategies and programs developed through this project clearly attest to its success.
In 2012, 5 yr-old red grapefruit trees in an 11 acre trial block surrounded by a 20-30 ft tall Corymbia torelliana windbreak averaged 50 % less canker infected fruit in copper sprayed trees than in the non-sprayed trees. In an adjacent block with the same windbreak system, weather stations were deployed in east-west and north-south directions to measure the effect of proximity to the windbreak on wind speed expressed as the number of wind gusts ’11 mph (5 m/sec) and the relationship with incidence of fruit lesions. As predicted from previous simulations of the effect of wind on bacterial infection, the greater the exposure to wind, the higher the canker fruit incidence. The number of wind gusts ’11 mph increased with distance from the windbreak whether measured within the north to south rows or across the rows from east to west. Therefore, the highest fruit disease (~10%) was in the center of the 11 acre block and the lowest incidence (~2%) was the east-west row location nearest the windbreak. Consistent with previous trials in Florida as well as in Brazil and Argentina, the effectiveness of the protective film of copper on fruit did not vary greatly among standard copper formulations applied at 2 to 4 lb/acre of product (0.75 to 1.4 lb/acre of metallic copper). Nordox’ (copper oxide, 75% metallic) at 0.44 lb/acre, 30% of the 1.33 lb/acre (1.0 lb metallic) rate, combined with Magna-Bon’ at 100 ppm/acre was as effective as 1.33 lb of Nordox’. Alternatively, application of Nordox at 1.33 lb/acre for the first 5 sprays followed by 5 sprays of Magna-Bon’ at 100 ppm/acre was also as effective as the full rate of Nordox’ season-long. These mixtures or alternations of copper formulations amount to 50% less metallic copper per season which represents a substantial reduction in copper loading of the grove soil considering that 10-11 sprays are recommended to protect grapefruit until full expansion. In 2011, our trial of 4 yr-old Hamlins suffered 70% fruit drop in the non-sprayed trees due to intense rains in April and May. Even with copper sprays, the losses were reduced to ~40% fruit drop which is an unacceptable level of control. This outcome emphasizes the importance of early season spray timing in relation to fruit size and the application of a formulation or mixture of formulations with sufficient metallic copper to protect the fruit. In 2012, April and May were relatively dry and sprays were stopped early in July as recommended (after 4-5 sprays). Although the incidence of new canker lesions exceeded 30-40% in copper treatments by the end of season, these late season lesions caused only minor fruit drop. Similar to the results with grapefruit, a mixture of Magna-Bon at 100 ppm/acre with a rate of Nordox’ reduced to 30% of the standard rate (0.44 lb/acre) was as effective as the full rate with only 50% of the metallic copper per application. Likewise, protecting fruit with Nordox’ early in the season in the first 3 sprays followed by 2 sprays of Magna-Bon’ was as effective as 5 sprays of the full rate of Nordox’. Recently completed studies identified the potential for development of copper resistance in Xcc after long-term use in citrus groves. Use of FireWall’ (AgroSource, Inc.) is effective for canker control on grapefruit and reduces the risk of copper phytotoxicity to fruit, and possibly for development of copper resistance in Xcc. In September 2012, FireWall’ received a Section 18 Emergency Use Exemption from EPA for use against canker on fresh grapefruit. Use is limited to two applications per season at 2 lb/acre per application. FireWall may be used based upon advice from experts, particularly at the critical time for fruit infection during tropical weather conditions. Thus far, canker control on leaves and fruit for soil applied SAR inducers, including Admire Pro’, Platinum’, Belay’, Actigard’ and a new insecticide for aphids, psyllids and whiteflies called Sivanto’ (nAChR Agonist /Butenolide; Bayer Crop Science) is equivalent to season long 21-day interval sprays of Kocide’ 3000. Actigard’ is not yet registered for use on citrus but we are currently working with Syngenta under an EPA experimental use permit (EUP) to develop efficacy data to support registration for young bearing grapefruit trees in an integrated canker management program with copper sprays.
Objective 1: Assays of non-bearing trees indicate that soil drench is an effective and consistent application method for increasing copper status of young leaves well above the baseline concentration. The preventative and curative activity of the copper bactericides are being followed in pre- and early stage HLB infected trees. In a trial located at Picos Farm in USDA-Ft. Pierce, Hamlin on Swingle citrumelo trees were root drenched with the copper bactericides: EXP, Cop-R-Quik, (CQ) Magna-Bon (MB), copper phosphite (CP) and zinc phosphite (ZP). In two other locations in ridge groves, healthy pre-bearing trees were drenched with copper chelates (CQ and MB). All three locations were assayed for HLB status this past winter. Thus far, insufficient HLB positive trees have been detected in the non-treated checks to measure treatment effects. A trial in a block of 4-yr old Valencia trees with symptomatic and pre-symptomatic HLB infection as determined by PCR status, no effect of MB or CQ on HLB decline rating was detected in December 2012. Samples for PCR status of the trees in all trials will be collected and analyzed this fall.
During winter/spring 2013, we monitored 5 trials for citrus leafminer (CLM) suppression and a 6th trial on CLM movement. In 2012, unexpected failures of SPLAT CLM related to wax ingredients interfered with pheromone stability. With ISCA Technologies, we immediately began testing solid rubber dispensers manually attached to trees, with astounding success. It now appears feasible to obtain season-long disruption of CLM with a single application of pheromone dispensers, greatly reducing cost of mating disruption. Timing of application is less critical providing growers with flexibility. We are working with ISCA to test their new product, DCEPT CLM’ to determine optimal formulation and deployment strategies. Trial 1: Winter/spring deployment (The Packers of Indian River). Winter/spring application of rubber dispensers in a split-plot factorial with 4 blocks. Dispensers loaded with triene (338 mg/ac) deployed Feb 6-8; spring application planned for Apr 17. Trap catch disruption (TCD) was 97% after 8 wks. On 30 Jan, 2% of shoots were infested. On 26 Mar, none of the shoots collected was infested. The number of new flush shoots present was greater at the second evaluation. Trials 2-3: Solid dispensers (St. Lucie Co., Golden River Fruit Co.) We monitored TCD in 0.35 ac plots treated with rubber dispensers (130/ac) loaded with ‘natural’ 3:1 blend or triene only. TCD was 82% (blend) and 85% (triene) after 39 wks. Moth flight is now abundant (10 April) with 66 moths/trap/d in untreated plots. Data suggests both formulations work by non-competitive disruption. A 168 ac plot was treated with natural blend pheromone dispensers on 24 Aug, providing 99% TCD at 32 wks (7.5 months) with 10 males/trap/d in untreated plots. Trial 4: Large plot test of solid dispensers (The Packers of Indian River). An experiment began in Sept 2012 to compare TCD in 2.15 acre plots treated with dispensers containing natural blend (134 dispensers/acre) to untreated plots. TCD was >95% at 26 wks with moth numbers now reaching 44 moths/trap/d in untreated plots. Trial 5: Large plot solid dispensers (Charlotte Co., TRB Groves). We monitored a grower validation trial treated on 20-23 Aug (104 ac) with solid dispensers (natural blend). TCD was >99% after 39 wks. Trial 6: Movement of CLM (St. Lucie Co., Blue Goose Growers). A new experiment tests how far CLM flies to traps in grassland at 75, 150, 300, 600, and 1,200 meters along a transect west of a grove (source of CLM). We will also test infestation of potted citrus sentinel plants along similar transects adjacent to the CLM source. Trial 7 (planned): Attraction of CLM and nontarget Phyllocnistis spp to ternary and binary pheromone blends (St. Lucie Co.). Several Phyllocnistis species were attracted to lures containing 3:1 triene:diene binary blend in CLM lures. In addition to the triene and diene, pheromone glands of female CLM produce a monoene that is unnecessary for CLM attraction. We will test our hypothesis that the monoene compound plays a role in interspecific recognition. Trial 8 (planned): Trap catch disruption of CLM in young trees. We will test rubber dispensers’ ability to disrupt trap catch in open canopy plantings of young trees. TCD and leaf mining will be evaluated. Manuscript accepted. ‘Attraction of a Native Florida Leafminer, Phyllocnistis insignis (Lepidoptera: Gracillariidae), to Pheromone of an Invasive Citrus Leafminer, P. citrella: Evidence for Mating Disruption of a Native Nontarget Species’ was was accepted for publication in Florida Entomologist.
Using coupled gas chromatograph-couples electroantennography, we previously discovered two compounds produced from degraded primary citrus volatiles that were found to stimulate the antennae of Asian citrus psyllids. These compounds are neither constitutive (primary) volatiles nor induced volatiles, two classes of host plant semiochemicals that are well-known and continue to be of great interest to chemical ecologists. In subsequent testing of these unique citrus volatile degradation products, we observed a phenomenon never seen previously in the psyllid family: sexual dimorphism in antennal sensitivity to volatile compounds. We used the two newly discovered compounds to test the antennal responses of male and female psyllids in a log dose manner. In this trial, the chemicals were presented in six doses which included 200 ng, 2 ug, 20 ug, 0.2 mg, 2 mg and 20 mg and a solvent only control. Only one of the compounds yielded responses that were significantly greater from female psyllid antennae than from male psyllid antennae at all doses tested. We will pursue this information to assess if there are differences in behavioral response as well.
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