Citrus plants and forestry species were set at the same planting line. Row spacing between lines was 5 meters and between plants 2 meters. It was observed that plants with up to 70% shading around noon showed reduction in the development of symptoms of HLB with values between 5% affected canopy and 8% , while in without shading presented 18% of the canopy with symptoms. The incidence of the disease was also lower in citrus plants in the shaded areas , while in the area without shading was 97%. The data were subjected to analysis of variance and, when detected significant difference, were compared by Duncan.Huanglongbing caused by the bacterium Liberibacter asiaticus is the most devastating disease of citrus in the United States today. Current methods for identifying infected trees include scouting for symptoms in the field and detection of Las by quantitative PCR in samples from suspected trees. However, because infected trees may appear asymptomatic and come up negative with qPCR, given the typically focal nature of the infection, there is a great and urgent need for additional detection methods. We describe here an indirect detection method based on Las-induced systemic changes in the microbiota of citrus trees following infection with Las but prior to symptom formation. More specifically, the method entails swabbing citrus leaves, extracting microbial DNA from the swabs, PCR amplifying the bacterial 16S and fungal ITS regions, sequencing using the Illumina platform, and analyzing the data using QIIME,dutch bucket hydroponic a microbial community analysis pipeline. A combination of ordination techniques and taxon abundance rules are then used to call a tree positive, negative, or suspect.

The method has been successfully used to distinguish infected trees from non-infected ones in greenhouse experiments at UC Davis and under field conditions in Texas. Our method is currently being optimized for deployment under California field conditions. This work proposes a simulation model that evaluates the impacts on production and on the citrus plantations depending on the level of infection and the spread of huanglongbing . We used the Individual Based Modeling methodology. In this model, we considered the invasion of psyllids from neighboring orchards and scenarios where the orchard performs the sanitary management, i.e. roguing symptomatic citrus plants and replanting healthy trees. The productivity of citrus trees was calculated through the model defined by Bassanezi RB and Bassanezi RC , which made possible to obtain the orchard yield depending on the incidence of HLB. The productivity and costs depend on the age of the plant, the sanitary management and the epidemiological states. To analyze the impact on orchard yield was made a simplified calculation of cash flow. The sanitary management is guided by the Normative Instruction of Brazilian Ministry of Agriculture, Livestock and Food Supply, which recommend to the citrus farmers to perform the inspection in an orchard every 3 months and roguing symptomatic plants.It is known that the primary means of attraction and reproduction of psyllids is through the shoots of plants, in which the deposition of eggs is made only in young plant tissues. Older plants and young can have different levels of flush, what results in different levels of attraction to the vectors of diseases. The simulation results show an increase of the yield and a lower disease incidence with the sanitary management in long-term. Other contribution of this work is the easy way to change the many parameters and scenarios in the model.

Hamlin and Valencia oranges were each harvested twice per year for two growing years in Lake Alfred, FL and processed into cold pressed oils. During each harvest, both asymptomatic and symptomatic fruit were sampled. There was one sampling early in each orange’s harvest season and a second sampling late in the harvest season. The oils underwent several quality tests including US Pharmacopeia mandated physiochemical tests ; taste panels; aroma panels; and qualitative and quantitative gas chromatography. Overall results showed both symptomatic and asymptomatic Hamlin oils had aldehyde contents below the US Pharmacopeia minimum for both harvest years. For Hamlin oranges harvested in the early season harvest for the 2015- 2016 season, there were significant differences between symptomatic and asymptomatic oils for aldehyde content, specific gravity, UV absorbance, and optical rotation. There were no significant differences between solutions made with Hamlin asymptomatic and symptomatic oils in taste panels. However, there were significant differences between early season Hamlin asymptomatic and symptomatic oils in aroma panels. Several differences were seen between asymptomatic and symptomatic Valencia oils for the US Pharmacopeia tests for both the 2014-2015 and 2015-2016 harvest seasons. Additionally, late season symptomatic Valencia oils exceeded the US Pharmacopeia maximum for specific gravity for both years. There were no significant differences between solutions made with Valencia asymptomatic and symptomatic oils in taste panels. However, there were significant differences between late season Valencia asymptomatic and symptomatic oils in aroma panels. Quantitative gas chromatography showed that multiple compounds important to orange aroma and flavor which are significantly different between asymptomatic and symptomatic samples for both Hamlin and Valencia oils. These compounds include decanal, linalool, citronellal, citronellol, neral, and geranial. The aroma panel results and decrease in concentration of these important orange aroma compounds show that HLB may have a negative effect on cold pressed Hamlin and Valencia oils. The Asian Citrus Psyllid Diaphorina citri Kuwayama, was detected on March 2006, on citrus plants in the residential area of Ciudad Obregon Sonora, one year later it was observed in Guaymas and Hermosillo, Sonora.

Since its discovery in Ciudad Obregon, surveys were carried out in order to determine its regional dispersion and migration to citrus commercial plantations. In 2010 an area-wide strategic management plan was established. The main objective was to keep ACP populations at the minimum level and lower the risk of HLB establishment in the state of Sonora. This plan continues until now and it has been successful in keeping ACP populations at very low levels and no HLB on citrus plants, have been detected. The plan is based in a coordinated effort and mandatory actions in commercial plantations including weekly surveys by yellow sticky traps and tap sampling, two area-wide insecticide applications are made one in the dormant stage and other in the fall , besides during the growing season if monitoring indicates that an orchard is over the regional ACP population mean it is considered as hot spot and recommended for control. Citrus plants in rural and residential areas are also monitored and sprayed to reduce the ACP population at the regional level. Results of the area-wide management plan are considered satisfactory after ten years of the first detection of ACP in Sonora. Considerable reduction in ACP populations has been achieved and not HLB plants have been detected on the surveys realized. However, in the last two years HLB infected Psyllids were detected in rural areas of Southern Sonora and an aggressive action plan was implemented controlling ACP populations and eliminating citrus plants in the area were these infective Psyllids were observed. Further surveys and psyllid analysis for HLB have not shown any more infected insects or citrus plants in the area. Surveillance activities play an integral part in disease prevention and control, and underpin the three main stages of disease mitigation: the prevention of entry and establishment of exotic pathogens; the detailed investigation of more established pathogens; and the monitoring of disease control measures. As with any disease mitigation measure, it is important that surveillance activities are planned, implemented,dutch buckets system and evaluated using scientifically valid approaches. This process of “survey validation” allows us to ensure that surveillance schemes are performing satisfactorily , and allows appropriate adjustments to be made to improve survey performance and efficiency. Whilst survey validation is best achieved using a systematic methodology, the range of different surveillance aims in different settings means that this methodology must also be flexible. One way to achieve a suitable balance of structure and flexibility is to identify specific attributes of the surveillance aims as part of the validation process, which can then be used to determine which precise validation approaches are most appropriate. Although HLB is a threat to the citrus industry throughout the USA, its impact upon the industry to date at the state level has varied. In Florida, HLB is thought to be well established throughout all commercial orchards; in Texas, it has been reported in some orchards but at lower levels than in Florida; and in California, the disease has not yet been detected in commercial orchards. As a result of this variation, the surveillance activities in place differ between the three states. We use a recently developed survey validation framework to evaluate these HLB surveillance activities. Since our approach allows the different epidemiological scenarios in each state to be explicitly accounted for within the context of a standardised framework, strengths and weaknesses of the different surveillance schemes can be better identified. Many citrus production areas are currently threatened by HLB. Whilst minimising the risk of spread of the HLB bacterium and insect vector are important strategies for reducing the risk of HLB entry, there will always be a potential risk of introduction. This means that effective early detection surveillance activities – focussed at detecting Las infection at an early stage – must be in place. Our previous work has demonstrated that the epidemiology of a pathogen should be considered when developing surveillance strategies.

The presence of insect vectors as well as host plants in the HLB pathosystem adds another layer of complexity to the issue of surveillance, since it leads to the question of whether to sample from hosts, vectors, or both. Although this question has considerable implications for the design of the surveillance strategy, many surveillance schemes focus on sampling from host plants, with vectors sampled more opportunistically. To investigate this issue further, we have developed a statistical model of host and vector sampling and linked this to a mathematical model of pathogen transmission through the HLB pathosystem as a whole. The resultant model allows us to quantify the relative sampling efforts and/or costs required from hosts and vectors in order to detect a specified incidence of infection in either. From this, we demonstrate that the overall incidence at first detection is minimised when samples are exclusively collected from either hosts or vectors but not from both. As well as identifying whether hosts or vectors should be sampled, our method gives a numerical output which indicates how robust this decision is to changes in sampling costs. This has potential for use as a simple tool to determine where best to place sampling resources whilst accounting for both epidemiological issues and economic constraints. Sweet oranges have little resistance to HLB, a disease presumably caused by Canadidatus Liberibacter asiaticus . As HLB has become widespread in Florida over ten years, we have very carefully followed the extensive collections of our breeding materials including mutants and germplasm accessions within the UF-CREC citrus breeding program. We have found that two 13 year-old Valencia clones and one Kansu orange are apparently tolerant to HLB. All multiple propagations of three clones have been rejuvenated by continual vigorous growth of new shoots with few foliar and fruit symptoms. In this study, we used comparative transcriptional and anatomical analyses to evaluate gene expression and anatomical differences between three tolerant Valencia types and a susceptible standard Valencia. Underlying tolerance mechanisms revealed by RNAseq and anatomical analysis will be described. The results potentially lead to identification of key genes and the genetic mechanism in irradiated Valencia to restrain disease development. The psyllid Diaphorina citri is the vector of the bacteria associated with huanglongbing , which is the most destructive citrus disease worldwide. Chemical control is the primary tactic against this insect. However, alternative methods are important to achieve a more effective control in an integrated pest management programs. Thus, this research was carried out to assess the influence of different kaolin formulations on the settling and probing behavior of D. citri. In both studies, two wettable powder kaolin formulations were sprayed three times at different concentrations on sweet orange plants. In the experiment to assess the settling behavior, three concentrations of both formulations were tested. A non-choice test was performed, where 16 adult psyllids were released in a cage with seedlings of the same treatment, and the number of psyllids/plant at different time intervals was counted. For the probing trial, the electrical penetration graph technique was used.