Diaphorina Citri Research Articles

An optical system to detect, surveil, and kill flying insect vectors of human and crop pathogens

Sustainable and effective means to control flying insect vectors are critically needed, especially with widespread insecticide resistance and global climate change. Understanding and controlling vectors requires accurate information about their movement and activity, which is often lacking. The Photonic Fence (PF) is an optical system that uses machine vision, infrared light, and lasers to identify, track, and interdict vectors in flight. The PF examines an insect’s outline, flight speed, and other flight parameters and if these match those of a targeted vector species, then a low-power, retina-safe laser kills it. We report on proof-of-concept tests of a large, field-sized PF (30 mL × 3 mH) conducted with Aedes aegypti, a mosquito that transmits dangerous arboviruses, and Diaphorina citri, a psyllid which transmits the fatal huanglongbing disease of citrus. In tests with the laser engaged, < 1% and 3% of A. aegypti and D. citri, respectfully, were recovered versus a 38% and 19% recovery when the lacer was silenced. The PF tracked, but did not intercept the orchid bee, Euglossa dilemma. The system effectively intercepted flying vectors, but not bees, at a distance of 30 m, heralding the use of photonic energy, rather than chemicals, to control flying vectors.

Addition of Selected Plant-Derived Semiochemicals to Yellow Sticky Traps Does Not Improve Citrus Psyllid Captures

Fast and effective monitoring and surveillance techniques are crucial for the swift implementation of control methods to prevent the spread of Huanglongbing, a devastating citrus disease, and its invasive psyllid vector, Asian citrus psyllid, Diaphorina citri, into South Africa, as well as to control the native vector, African citrus triozid, Trioza erytreae. Monitoring for citrus psyllid pests can be improved by using semiochemical odorants to augment already visually attractive yellow sticky traps. However, environmental variables such as temperature and humidity could influence odorant release rates. Five field cages were used to test the ability of a selection of odorants to improve yellow sticky trap efficacy in capturing citrus psyllids. Environmental effects on odorant loss from the dispensers were also investigated. The odorants that most improved yellow sticky trap captures in field cages were then tested under open field conditions alongside lower concentrations of those same lures. Gas chromatography-mass spectrometry was used to calculate odorant release rates as well as to determine if any contamination occurred under field conditions. None of the odorants under field cage or field conditions significantly improved psyllid capture on yellow sticky traps. Temperature influenced odorant loss, and release rate from polyethylene bulbs decreased over time. Based on these results, the use of unbaited yellow sticky traps seems to be the most effective method for monitoring of Huanglongbing vectors.

Identification and characterization of two P450 enzymes from Citrus sinensis involved in TMTT and DMNT biosyntheses and Asian citrus psyllid defense.

The homoterpenes (3E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT) are the major herbivore-induced plant volatiles that help in defense directly by acting as repellants and indirectly by recruiting insects' natural enemies. In this study, DMNT and TMTT were confirmed to be emitted from citrus (Citrus sinensis) leaves infested with Asian citrus psyllid (Diaphorina citri Kuwayama; ACP), and two cytochrome P450 (CYP) genes (CsCYP82L1 and CsCYP82L2) were newly identified and characterized. Understanding the functions of these genes in citrus defense will help plan strategies to manage huanglongbing caused by Candidatus Liberibacter asiaticus (CLas) and spread by ACP. Quantitative real-time PCR (qPCR) analysis showed that CsCYP82L1 and CsCYP82L2 were significantly upregulated in citrus leaves after ACP infestation. Yeast recombinant expression and enzyme assays indicated that CsCYP82L1 and CsCYP82L2 convert (E)-nerolidol to DMNT and (E,E)-geranyllinalool to TMTT. However, citrus calluses stably overexpressing CsCYP82L1 generated only DMNT, whereas those overexpressing CsCYP82L2 produced DMNT and TMTT. Furthermore, ACPs preferred wild-type lemon (Citrus limon) over the CsCYP82L1-overexpressing line in dual-choice feeding assays and mineral oil over TMTT or DMNT in behavioral bioassays. Finally, yeast one-hybrid, electrophoretic mobility shift, and dual luciferase assays demonstrated that CsERF017, an AP2/ERF transcription factor, directly bound to the CCGAC motif and activated CsCYP82L1. Moreover, the transient overexpression of CsERF017 in lemon leaves upregulated CsCYP82L1 in the absence and presence of ACP infestation. These results provide novel insights into homoterpene biosynthesis in C. sinensis and demonstrate the effect of homoterpenes on ACP behavior, laying a foundation to genetically manipulate homoterpene biosynthesis for application in huanglongbing and ACP control.

Trunk Injection of Citrus Trees with a Polymeric Nanobactericide Reduces Huanglongbing Severity Caused by Candidatus Liberibacter asiaticus.

Huanglongbing (HLB) is a disease caused by the phloem- limited Candidatus Liberibacter asiaticus (CLas) that affects the citrus industry worldwide. To date, only indirect strategies have been implemented to eradicate HLB. Included among these is the population control of the psyllid vector (Diaphorina citri), which usually provides inconsistent results. Even though strategies for direct CLas suppression seem a priori more promising, only a handful of reports have been focused on a confrontation of the pathogen. Recent developments in polymer chemistry have allowed the design of polycationic self-assembled block copolymers with outstanding antibacterial capabilities. Here, we report the use of polymeric nano-sized bactericide particles (PNB) to control CLas directly in the phloem vasculature. The field experiments were performed in Rioverde, San Luis Potosí, and is one of the most important citrusproducing regions in Mexico. An average 52% reduction in the bacterial population was produced when PNB was injected directly into the trunk of 20 infected trees, although, in some cases, reduction levels reached 97%. These results position PNB as a novel and promising nanotechnological tool for citrus crop protection against CLas and other related pathogens.

Identification and Distribution of the 'Candidatus Liberibacter asiaticus'-Asian Citrus Psyllid Pathosystem in Saudi Arabia.

Citrus greening disease was first reported in Saudi Arabia during the 1970s when characteristic foliar and fruit symptoms were observed in commercial citrus groves. However, 'Candidatus Liberibacter asiaticus' (CLas) was not detected in symptomatic trees until 1981 to 1984 when CLas-like cells were observed by transmission electron microscopy in leaves collected from symptomatic citrus groves in southwestern Saudi Arabia. Despite the anticipated establishment of the CLas-Asian citrus psyllid (ACP) (Diaphorina citri Kuwayama) pathosystem, CLas presence has not been verified in suspect trees nor have ACP infestations been documented. Given the recent expansion of citrus production in Saudi Arabia, a systematic country-wide survey was carried out to determine the potential CLas distribution in the 13 citrus-growing regions of the country. Citrus trees were surveyed for the presence of CLas-psyllid vector(s) and characteristic disease symptoms in commercial and urban citrus trees. Adult psyllids collected from infested citrus trees were identified as ACP based on morphological characteristics. Real-time quantitative PCR amplification (qPCR) of the CLas β-subunit of the ribonucleotide reductase (RNR) gene from citrus leaf and fruit samples and/or ACP adults revealed that trees were positive for CLas detection in 10 of the 13 survey regions; however, CLas was undetectable in ACP adults. Phylogenetic and single nucleotide polymorphism (SNP) analyses of a PCR-amplified, cloned fragment of the CLas 16S rRNA gene (∼1.1 kbp) indicated Saudi Arabian isolates were most closely related to Florida, U.S.A., isolates. Analysis of climate variables indicated that the distribution of the ACP-CLas pathosystem observed in Saudi Arabia was consistent with published predictions of terrains most likely to support establishment.

Guardians of Citrus Groves: An In-Depth Analysis of Neem Leaf Extract's Effects on Asian Citrus Psyllid Attractiveness, Diaphorina citri kuwayama, And its Potential for Integrated Pest Management

Background: The pervasive impact of fungal diseases on wheat crops necessitates the exploration of sustainable and safe pest control alternatives. Neem (Azadirachta indica) is renowned for its medicinal properties and is being investigated for its potential as a biopesticide in agriculture. Objective: To evaluate the antifungal efficacy of Azadirachta indica leaf extracts on fungal pathogens in wheat crops, aiming to offer an environmentally benign alternative to chemical fungicides. Methods: Neem leaves were collected, sterilized, dried, and ground to powder. This powder was subjected to solvent extraction using methanol, diethyl ether, chloroform, petroleum ether, and distilled water. The resulting extracts were tested for antifungal activity against Diaphorina citri kuwayama using the agar well diffusion method. Wheat plants treated with the extracts were monitored for fungal disease incidence and yield changes. Results: Methanolic extracts of Azadirachta indica showed a significant zone of inhibition of 34.67 mm against Diaphorina citri kuwayama. Additionally, methanolic extracts displayed a zone of inhibition of 31.6±2.04 mm, while the control showed 31.33±0.58 mm. The MIC values ranged from 35 µg/ml for methanol to 24 µg/ml for distilled water, with the control at 20 µg/ml. Treatment of wheat crops with these extracts resulted in reduced fungal contamination and enhanced yield. Conclusion: The study confirms that Azadirachta indica leaf extracts have substantial antifungal properties, demonstrating potential as a natural and environmentally friendly pest management strategy in wheat production. This approach aligns with sustainable agricultural practices and could have a beneficial impact on human health by reducing harmful chemical residues in food.

The Amino Acid Transporter PtCAT7 and Ammonium Nutrition Enhance the Uptake of Thiamethoxam in Citrus Rootstock Seedlings.

Thiamethoxam (THX), when applied to the soil, can be taken up by citrus roots and subsequently transported to the leaves, providing effective protection of plants against the Asian citrus psyllid (Diaphorina citri Kuwayama). In this study, the field experiments showed that the coapplication of THX and nitrogen fertilizer (AN) did not affect THX uptake in six-year-old citrus plants. However, their coapplication promoted THX uptake in three-year-old Potassium trifoliate rootstocks and relieved the inhibition of AN at a higher level on plant growth characteristics, including biomass and growth of root and stem. RNA-seq analysis found that THX induced upregulation of a cationic amino acid transporter (PtCAT7) in citrus leaves. PtCAT7 facilitated THX uptake in the yeast strain to inhibit its growth, and the PtCAT7 protein was localized on the plasma membrane. Our results demonstrate that THX and N fertilizer can be coapplied and PtCAT7 may be involved in THX uptake in citrus.

Transcriptomic response of citrus psyllid salivary glands to the infection of citrus Huanglongbing pathogen.

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is the key vector insect transmitting the Candidatus Liberibacter asiaticus (CLas) bacterium that causes the devastating citrus greening disease (Huanglongbing, HLB) worldwide. The D. citri salivary glands (SG) exhibit an important barrier against the transmission of HLB pathogen. However, knowledge on the molecular mechanism of SG defence against CLas infection is still limited. In the present study, we compared the SG transcriptomic response of CLas-free and CLas-infected D. citri using an illumine paired-end RNA sequencing. In total of 861 differentially expressed genes (DEGs) in the SG upon CLas infection, including 202 upregulated DEGs and 659 downregulated DEGs were identified. Functional annotation analysis showed that most of the DEGs were associated with cellular processes, metabolic processes, and the immune response. Gene ontology and Kyoto Encyclopaedia of Genes and Genomes enrichment analyses revealed that these DEGs were enriched in pathways involving carbohydrate metabolism, amino acid metabolism, the immune system, the digestive system, the lysosome, and endocytosis. A total of 16 DEGs were randomly selected to further validate the accuracy of RNA-Seq dataset by reverse-transcription quantitative polymerase chain reaction. This study provides substantial transcriptomic information regarding the SG of D. citri in response to CLas infection, which may shed light on the molecular interaction between D. citri and CLas, and provides new ideas for the prevention and control of citrus psyllid.

Vesicular transport-related genes in Diaphorina citri are involved in the process of Candidatus Liberibacter asiaticus infection

Asian citrus psyllid (ACP, Diaphorina citri) is the major vector of Candidatus Liberibacter asiaticus (CLas), which is a bacterial pathogen causing the devastating citrus Huanglongbing (HLB) disease. Diaphorina citri is known to carry CLas in a persistent and propagative manner. Some studies have suggested that CLas may use the vesicular structures of D. citri cells as its propagation organelles. However, the mechanisms by which CLas enters the D. citri cells and how vesicle-mediated trafficking is involved remain unclear. In this study, we monitored the titer change of CLas in D. citri nymphs during the process of CLas acquisition from feeding on infected citrus plants. We found that the titer of CLas increased with the acquisition access period. After infection, there was a significant upregulation in the expression of several vesicular transport-related genes in D. citri. The titer of CLas was significantly reduced in the midgut and whole insect body when endocytosis and the endosome network in D. citri were inhibited. Furthermore, silencing the D. citri clathrin-heavy chain gene also led to a reduction in the CLas titer in D. citri. These results suggest that CLas infection upregulates the genes related to vesicular transport in D. citri, which facilitates the invasion of endocytosis-dependent pathogens.

Improvement of the production and quality of Cordyceps javanica conidia for the control of Diaphorina citri adults.

This study aimed to evaluate the use of palm kernel meal (PKM) in the traditional solid-state fermentation system to improve the production and quality of Cordyceps javanica conidia. The impact of PKM was determined by measuring conidia yield, viability, hydrophobicity, shelf life, and conidia pathogenicity against Diaphorina citri adults. By supplementing rice grains with 5% palm kernel meal increased the conidial yield by up to 40%, without compromising conidia viability and hydrophobicity. In addition, conidia caused higher levels of mortality by mycosis against D. citri adults (90%), relative to conidia harvested from rice (52%). The conidia recovered from rice/palm kernel meal mixtures also retained viability greater than 90% after storage for 10months at 4°C, while the conidia produced on rice reached 80%. Thus, conidia produced in the presence of palm kernel meal can be consumed immediately or in the medium term. Some process advantages of the palm kernel meal as co-substrate in the traditional production system of C. javanica are also mentioned. These results are attractive for improving the mycoinsecticide production process, with excellent cost-benefit and minimal changes in infrastructure and process.

Uncovering the presence of CVPD disease in citrus varieties of South Sulawesi, Indonesia: A molecular approach

BackgroundThe citrus vein phloem degeneration (CVPD) disease is one of important diseases that infects citrus plants and threatens global citrus production and quality due to its severe symptoms and rapid spread. In the 2000s, South Sulawesi Province as one of the citrus producers in Indonesia reported CVPD infection. To date, it is still uncertain as to whether the citrus production center has already been rid of the CVPD infection, keeping in mind the low prevalence of certified citrus saplings use and sub-optimal management of plantations by farmers. ResultsField observation results revealed varied chlorosis symptoms from young to productive cultivation, which certainly makes it appealing to find out the presence of the causative bacterium, as it has yet to be known whether all the leaves with positive chlorosis symptoms carry the bacterium Candidatus Liberibacter asiaticus. Citrus saplings that appear healthy may carry CVPD pathogens as the incubation period of CVPD pathogens in the host plant spans three to five months. Thus, it is necessary to find the right, rapid way to detect the presence of CVPD pathogens in the citrus plant. The most effective method to use is PCR as the bacterium Candidatus L. asiaticus is non-culturable in vitro, but it is detectable using 16S rDNA. Sampling of leaves with CVPD symptoms was conducted purposively from eight varieties in five citrus cultivation locations, i.e., Pangkep, Sidrap, Bantaeng, Luwu Utara, and Kepulauan Selayar Regencies. DNA isolation was carried out following the Genomic DNA Kit (Geneaid) procedure, followed by detection using the specific pathogenic primer pair OI1 (5′ GCG CGT ATG CAA TAC GAG CGG C 3′) and OI2c (5′ GCC TCG CGA CTT CGC AAC CCA T 3′). ConclusionThe PCR visualization result shows seven positive samples with DNA fragments measuring 1160 bp. The seven samples were samples of the Key lime, tangerine, Mandarin (cv. batu 55), and Mandarin (cv. selayar), each being derived from Sidrap, Luwu Utara, and Bantaeng. The average disease incidence rate was 66.56 %. Based on the field observation results, the insect vector Diaphorina citri was nowhere to be found in the five citrus cultivation locations in South Sulawesi.

Longitudinal Transcriptomic, Proteomic, and Metabolomic Response of Citrus sinensis to Diaphorina citri Inoculation of Candidatus Liberibacter asiaticus.

Huanglongbing (HLB) is a fatal citrus disease that is currently threatening citrus varieties worldwide. One putative causative agent, Candidatus Liberibacter asiaticus (CLas), is vectored by Diaphorina citri, known as the Asian citrus psyllid (ACP). Understanding the details of CLas infection in HLB disease has been hindered by its Candidatus nature and the inability to confidently detect it in diseased trees during the asymptomatic stage. To identify early changes in citrus metabolism in response to inoculation of CLas using its natural psyllid vector, leaves from Madam Vinous sweet orange (Citrus sinensis (L.) Osbeck) trees were exposed to CLas-positive ACP or CLas-negative ACP and longitudinally analyzed using transcriptomics (RNA sequencing), proteomics (liquid chromatography-tandem mass spectrometry; data available in Dryad: 10.25338/B83H1Z), and metabolomics (proton nuclear magnetic resonance). At 4 weeks postexposure (wpe) to psyllids, the initial HLB plant response was primarily to the ACP and, to a lesser extent, the presence or absence of CLas. Additionally, analysis of 4, 8, 12, and 16 wpe identified 17 genes and one protein as consistently differentially expressed between leaves exposed to CLas-positive ACP versus CLas-negative ACP. This study informs identification of early detection molecular targets and contributes to a broader understanding of vector-transmitted plant pathogen interactions.

Arthropods and ultraviolet radiation: Survival, growth and development

Abstract Ultraviolet radiation (UVR) has positive and negative impacts on organisms and affects entire ecosystems. It is currently receiving attention because of the interactions of UVR with changes in climate that are likely to affect agriculture and food security. A review is provided on the effects of different types of UVR on the survival, development and reproduction of insects, collembolans and mites. The foci are on how UVR is used in pest control and how it affects arthropod coloration and distribution. Direct exposure to UV‐A, UV‐B and UV‐C delays development and reduces survival and host‐seeking ability of arthropods; immature stages are more sensitive than the adults. Increased exposure of crops to UVR has indirect effects on herbivory, and regions with high UVR levels may permit crop production in the absence of certain pest insect species. The Bunsen‐Roscoe law of reciprocity was upheld for Diaphorina citri and Tetranychus urticae under the range of irradiances and durations of exposure used in two studies, which showed that, for a constant dose, the effects of low irradiances of long durations were equivalent to those of higher irradiances of shorter durations. DNA damage caused by UV‐C and UV‐B can be repaired by photoreactivation; both white light and UV‐A are effective.

Detection of Candidatus Liberibacter asiaticus and five viruses in individual Asian citrus psyllid in China.

Asian citrus psyllid (ACP, Diaphorina citri) is an important transmission vector of "Candidatus Liberibacter asiaticus" (CLas), the causal agent of Huanglongbing (HLB), the most destructive citrus disease in the world. As there are currently no HLB-resistant rootstocks or varieties, the control of ACP is an important way to prevent HLB. Some viruses of insect vectors can be used as genetically engineered materials to control insect vectors. To gain knowledge on viruses in ACP in China, the prevalence of five RNA and DNA viruses was successfully determined by optimizing reverse transcription polymerase chain reaction (RT-PCR) in individual adult ACPs. The five ACP-associated viruses were identified as follows: diaphorina citri bunyavirus 2, which was newly identified by high-throughput sequencing in our lab, diaphorina citri reovirus (DcRV), diaphorina citri picorna-like virus (DcPLV), diaphorina citri bunyavirus (DcBV), and diaphorina citri densovirus-like virus (DcDV). DcPLV was the most prevalent and widespread ACP-associated virus, followed by DcBV, and it was detected in more than 50% of all samples tested. DcPLV was also demonstrated to propagate vertically and found more in salivary glands among different tissues. Approximately 60% of all adult insect samples were co-infected with more than one insect pathogen, including the five ACP-associated viruses and CLas. This is the first time these viruses, including the newly identified ACP-associated virus, have been detected in individual adult ACPs from natural populations in China's five major citrus-producing provinces. These results provide valuable information about the prevalence of ACP-associated viruses in China, some of which have the potential to be used as biocontrol agents. In addition, analysis of the change in prevalence of pathogens in a single insect vector is the basis for understanding the interactions between CLas, ACP, and insect viruses.

Bacillus thuringiensis translocation in citrus scion/rootstock combinations and binding of cry toxins with the Asian citrus psyllid gut receptors

Bacillus thuringiensis (Bt) can be effective in controlling insect pests either in spray products or by their toxins expressed in transgenic crops. The discovery of Bt as endophytic in citrus opened new perspectives for the control of Diaphorina citri Kuwayama, the vector of the bacteria Candidatus Liberibacter spp. associated with Huanglongbing. In this study, the endophytic translocation of Bt in citrus seedlings (small and large plants) and in different scion-rootstock combinations were investigated. We also assessed the lethal concentration of D. citri nymphs caused by systemic Bt in citrus and, moreover, the binding of Cry toxins with the Asian citrus psyllid (ACP) gut receptors. Endophytic translocation of Bt in citrus seedlings and nursery trees was confirmed by colony isolation, PCR detection, and Btk-GFP microscopy analyses, which demonstrated that, after Bt inoculation into the substrate, the bacteria enter through lateral root emergence sites and are localized in stem xylem vessel elements. Mean lethal concentrations for D. citri third instar nymphs were 4.92 × 104 and 2.19 × 104 spores mL−1 for S1450 and S1302 strains, respectively. Nymphal mortality induced by the bacteria was higher in citrus seedlings than in citrus nursery trees. All Cry-toxins tested were able to bind to D. citri brush border membrane vesicles, suggesting the potential pathogenicity of Bt strains against psyllid. This study clearly demonstrates the penetration and Bt translocation in the xylem of small and large citrus plants and the potential of the bacteria to cause ACP nymphs mortality that fed on shoots from Bt-treated citrus.

Ant community composition in a citrus grove reveals eastern expansion in Florida of the South American big-headed ant (Hymenoptera: Formicidae)

Abstract Florida has become a worldwide hotspot for introduced and invasive ants (Hymenoptera: Formicidae). Furthermore, studies have shown that non-native ants support other invasive insects in Florida, such as the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), which is the vector of Candidatus Liberibacter asiaticus, the causal pathogen of citrus greening, the worst citrus disease in the world. The Asian citrus psyllid establishes beneficial interactions with invasive, introduced, and native ants. In this study, we described the ant diversity in a citrus grove in south Florida as a first step to assess ant-Asian citrus psyllid interactions for future studies. During the summer of 2018, 25 pitfall traps were set in a citrus grove. The red imported fire ant, Solenopsis invicta (Buren), was present in all the traps (100 %), and 19 traps (76 %) had Dorymyrmex bureni (Trager), the pyramid ant, which is native to the southeast United States. Two introduced ants, Cardiocondyla emeryi (Forel) and Brachymyrmex obscurior (Forel), were found in 15 (60 %) and 11 (44 %) traps, respectively. The South American big-headed ant, Pheidole obscurithorax (Naves), was found in 14 traps (56 %). This introduced ant has been found to co-exist with S. invicta, and to our knowledge, this is the first report of the species in this eastern part of peninsular Florida. Finally, Cardiocondyla venustula (Wheeler), an introduced ant from Africa, was found in one of the traps. Although, this ant is found in south Florida, it seems uncommon, and this is its first report in this county. Our study highlights the continued spread of introduced and invasive ants in Florida.

Monitoring of coccinellid (Coleoptera) presence and syrphid (Diptera) species diversity and abundance in southern California citrus orchards: implications for conservation biological control of Asian citrus psyllid and other citrus pests

Abstract The abundance and diversity of three taxa of citrus pest predators, syrphids (Diptera), coccinellids (Coleoptera), and chrysopids (Neuroptera) and their association with flowering weed species in commercial citrus orchards in southern California were investigated. The occurrence and frequency of adult predators were determined with vertical yellow sticky traps and by performing 3 min visual counts on flowering weeds from May through November 2021. Syrphid abundance peaked in June and September, with the dominant species being Allograpta obliqua (Say), Toxomerus marginatus (Say), and Paragus tibialis (Fallen). Peak collections of coccinellids occurred in May, June, and September on sticky traps and during September and October in flowering weedy plants. Peak flowering of weed species occurred during May and declined sharply over summer into fall (June–November). The efficacy of yellow 355 mL glycol pan traps, yellow 1774 mL water pan traps, and yellow sticky traps orientated either horizontally or vertically with respect to capturing key natural enemies was evaluated in 2021 and 2022. Significantly more syrphids were captured on the horizontal yellow sticky traps than on the vertical yellow sticky traps or the yellow pan traps filled with glycol or water. Coccinellids were most frequently captured on vertical yellow sticky traps and yellow water pan traps. Numbers of chrysopids captured in all studies were not significant, which was most likely attributable to their nocturnal behavior. Collectively these results suggest that syrphid and coccinellid activity in southern California citrus orchards displayed two seasonal peaks, one in spring and the other in the fall. In the context of future conservation biological control, insectary plantings in spring (April–June) and fall (September–October) would be most beneficial to these predators and would coincide with population peaks of a key citrus pest, Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae).

Illustrating the current geographic distribution of Diaphorina citri (Hemiptera: Psyllidae) in Campeche, Mexico: a maximum entropy modeling approach

Abstract Diaphorina citri Kuwayama (Asian citrus psyllid) is a quarantine pest found in at least 60 countries, causing indirect damage as a primary vector of pathogens associated with Huanglongbing in citrus trees. Huanglongbing-infected trees die within 3–8 years, accompanied by economic losses in citriculture. D. citri has spread in Mexico to several states and is a high risk to Mexican citriculture due to its ability to cause damage and the lack of a disease cure. The primary objective of this research was to enhance our understanding of the current status of D. citri in southeastern Mexico. This study analyzed the distribution of D. citri in Campeche, Mexico from 2013 to 2020. The study generated 572,619 D. citri records from 40,620 yellow sticky traps deployed in 10 of the 12 municipalities of the state. We employed advanced MaxEnt and DivaGIS software to accomplish this study. Results showed population fluctuations with a peak during June and July from 2013 to 2019 and July and September in 2020. The study found a higher presence of D. citri in Campeche, Tenabo, Carmen, Champotón, and Escárcega and a higher incidence in Citrus latifolia Tanaka ex Q. Jiménez and Citrus sinensis (L.) Osbeck crops. The variance in the number of D. citri adults captured per year and the dispersion index (a parameter measuring the ability of insects to leave one ecosystem and move to another in search of suitable conditions for their survival and reproduction) was greater than the annual mean, demonstrating a spatially distributed, right-skewed aggregate. The elliptical polygon or standard deviation ellipse indicated the tendency for a less elongated ellipse in 2013–2014. From 2015 to 2018 D. citri expanded north towards Hecelchakán and south towards Champotón, Escárcega, and Carmen. In 2019, D. citri expanded north towards Champotón, Campeche, Tenabo, Hecelchakán, and Calkiní. The months with the most activity between 2013 and 2020 were May, June, July, and August, with June having the highest numbers collected. The results of the enveloped tests (parameter measuring how environmental conditions influence the spatial patterns of insect populations) showed the adaptability of D. citri to different conditions. D. citri prefers temperatures of 24.6–27.9 °C and 1,050–1,500 mm of rainfall. Areas with high-risk for D. citri are coastal and northern parts of the study area. Central Campeche is suitable, and southern parts have low to medium risk. Our research shows the relationship between climatic factors and the distribution of D. citri in the state of Campeche, Mexico. Moreover, our findings will be crucial for implementing effective surveillance measures in areas where the probability model indicates the potential presence of D. citri. This is especially significant due to the remarkable adaptability of D. citri to diverse environmental conditions.

Diversity of 'Candidatus Liberibacter asiaticus' Strains in Texas Revealed by Prophage Sequence Analyses.

Prophages/phages are important components of the genome of 'Candidatus Liberibacter asiaticus' (CLas), an unculturable alphaproteobacterium associated with citrus huanglongbing (HLB) disease. Phage variations have significant contributions to CLas strain diversity research, which provide critical information for HLB management. In this study, prophage variations among selected CLas strains from southern Texas were studied. The CLas strains were collected from three different CLas inhabitant environments: citrus leaf, citrus root, and Asian citrus psyllid (ACP), the vector of CLas. Regardless of the different habitats and time span, more than 80% of CLas strains consistently had both Type 1 and Type 2 prophages, the same prophage type profile as in CLas strains from Florida but different to those reported in California and China. Further studies were performed on prophage type diversity. Analyses on Type 1-specific PCR amplicon sequences (encoding an endolysin protein) revealed the presence of two groups: Type 1-A, clustered around prophage SC1 originating from Florida, and Type 1-B, clustered with prophage P-SGCA5-1 originating in California. Type 1-B strains were mostly from ACP of nearby citrus orchards. On the other hand, analyses on Type 2-specific PCR amplicon sequences (encoding a putative hypothetical protein) showed a single group clustering around prophage SC2 originated from Florida, although a different Type 2 prophage has been reported in California. The presence of two distinct Type 1 prophage groups suggested the possibility of two different CLas introductions in southern Texas. The results from this study provide an initial baseline of information on genomic and population diversity of CLas in Texas.

INCIDENDENCE OF GREENING IN THE REGION OF ARARAQUARA - SP

Huanglongbing (HLB) or greening is currently considered the disease with the greatest destructive potential in citriculture worldwide. Brazil is a large citrus producer, and HLB harms and puts the entire production chain of the crop in the country at risk, causing serious losses. The fall of symptomatic fruits and reduced quality and productivity can be highlighted as characteristics of this disease. The ability of the vector insect, the psyllid Diaphorina citri, to disperse between peripheral areas (borders), in addition to the ability of this pathogen to spread by insects developed on contaminated plants, demands organization for the management of disease control, making such an act very difficult. In this sense, the present work had as objective to evaluate the HLB indexes, in the total area of properties in the region of Araraquara, SP. Inspections were carried out on the reports provided by Fundecitrus and the data obtained were submitted to descriptive analysis to assess the frequency of occurrence of the disease. As a result, it was observed that sampling research is extremely important and efficient in combating the disease, especially at the beginning of its onset, allowing to conclude that is possible to control this disease when the management is adequate.